Add timezone-aware date filtering for reports page

- Add parse_timezone_offset() helper to parse timezone strings (UTC+3, Africa/Johannesburg, etc.)
- Add get_date_range_in_timezone() helper to calculate date ranges with proper timezone conversion
- Update reports(), export_reports(), client_report_detail(), match_report_detail(), export_client_report(), and export_match_report() to use timezone-aware date filtering
- Users can now select their timezone and date filters will correctly convert local time boundaries to UTC for database queries

app/main/routes.py

 import logging
 import os
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from flask import render_template, request, jsonify, redirect, url_for, flash, current_app
 from flask_login import login_required, current_user
 from app.main import bp
@@ -14,6 +14,197 @@ from flask import Response, make_response
 
 logger = logging.getLogger(__name__)
 
+
+def parse_timezone_offset(tz_string):
+    """
+    Parse a timezone string and return a timezone object.
+    Supports both named timezones (e.g., 'Africa/Johannesburg') and UTC offsets (e.g., 'UTC+3', 'UTC-5', 'UTC+5:30').
+    
+    Args:
+        tz_string: Timezone string (e.g., 'UTC+3', 'Africa/Johannesburg', 'auto')
+    
+    Returns:
+        A timezone object or None for 'auto' (should use browser timezone)
+    """
+    if not tz_string or tz_string == 'auto':
+        return None
+    
+    if tz_string == 'UTC' or tz_string == 'UTC+0':
+        return timezone.utc
+    
+    # Check if it's a UTC offset format (e.g., 'UTC+3', 'UTC-5', 'UTC+5:30')
+    if tz_string.startswith('UTC'):
+        offset_str = tz_string[3:]  # Remove 'UTC' prefix
+        if not offset_str:
+            return timezone.utc
+        
+        # Parse the offset
+        try:
+            # Handle formats like '+3', '-5', '+5:30', '-9:30'
+            if ':' in offset_str:
+                # Handle hours:minutes format
+                sign = 1 if offset_str[0] == '+' else -1
+                parts = offset_str[1:].split(':')
+                hours = int(parts[0])
+                minutes = int(parts[1]) if len(parts) > 1 else 0
+                total_minutes = sign * (hours * 60 + minutes)
+            else:
+                # Handle simple hour format
+                sign = 1 if offset_str[0] == '+' else -1
+                hours = int(offset_str[1:])
+                total_minutes = sign * hours * 60
+            
+            # Create a fixed offset timezone
+            return timezone(timedelta(minutes=total_minutes))
+        except (ValueError, IndexError):
+            logger.warning(f"Invalid UTC offset format: {tz_string}, defaulting to UTC")
+            return timezone.utc
+    
+    # Try to parse as a named timezone (e.g., 'Africa/Johannesburg')
+    try:
+        from zoneinfo import ZoneInfo
+        return ZoneInfo(tz_string)
+    except (ImportError, Exception) as e:
+        # Fallback for Python < 3.9 or invalid timezone names
+        logger.warning(f"Could not parse timezone '{tz_string}': {e}, defaulting to UTC")
+        return timezone.utc
+
+
+def get_date_range_in_timezone(date_range_filter, start_date_filter, end_date_filter,
+                                start_time_filter, end_time_filter, tz_string):
+    """
+    Calculate date range boundaries in the user's timezone and convert to UTC for database queries.
+    
+    Args:
+        date_range_filter: Date range type ('today', 'yesterday', 'this_week', 'last_week',
+                          'this_month', 'all', 'custom')
+        start_date_filter: Custom start date string (YYYY-MM-DD format)
+        end_date_filter: Custom end date string (YYYY-MM-DD format)
+        start_time_filter: Custom start time string (HH:MM format)
+        end_time_filter: Custom end time string (HH:MM format)
+        tz_string: Timezone string (e.g., 'UTC+3', 'Africa/Johannesburg')
+    
+    Returns:
+        Tuple of (start_date_utc, end_date_utc) as naive datetime objects for database queries
+    """
+    # Parse the timezone
+    tz = parse_timezone_offset(tz_string)
+    
+    # If no timezone specified or 'auto', use UTC (server default)
+    if tz is None:
+        tz = timezone.utc
+    
+    # Get current time in the user's timezone
+    now_utc = datetime.now(timezone.utc)
+    now_local = now_utc.astimezone(tz)
+    
+    start_date = None
+    end_date = None
+    
+    if date_range_filter == 'today':
+        # Start of today in user's local timezone
+        start_local = now_local.replace(hour=0, minute=0, second=0, microsecond=0)
+        end_local = now_local
+        
+        # Convert to UTC
+        start_date = start_local.astimezone(timezone.utc).replace(tzinfo=None)
+        end_date = end_local.astimezone(timezone.utc).replace(tzinfo=None)
+        
+    elif date_range_filter == 'yesterday':
+        # Start of yesterday in user's local timezone
+        yesterday_local = now_local - timedelta(days=1)
+        start_local = yesterday_local.replace(hour=0, minute=0, second=0, microsecond=0)
+        end_local = yesterday_local.replace(hour=23, minute=59, second=59, microsecond=999999)
+        
+        # Convert to UTC
+        start_date = start_local.astimezone(timezone.utc).replace(tzinfo=None)
+        end_date = end_local.astimezone(timezone.utc).replace(tzinfo=None)
+        
+    elif date_range_filter == 'this_week':
+        # Start of current week (Monday) in user's local timezone
+        days_since_monday = now_local.weekday()
+        start_local = now_local - timedelta(days=days_since_monday)
+        start_local = start_local.replace(hour=0, minute=0, second=0, microsecond=0)
+        end_local = now_local
+        
+        # Convert to UTC
+        start_date = start_local.astimezone(timezone.utc).replace(tzinfo=None)
+        end_date = end_local.astimezone(timezone.utc).replace(tzinfo=None)
+        
+    elif date_range_filter == 'last_week':
+        # Start of last week (Monday) in user's local timezone
+        days_since_monday = now_local.weekday()
+        last_week_end_local = now_local - timedelta(days=days_since_monday + 1)
+        last_week_start_local = last_week_end_local - timedelta(days=6)
+        
+        start_local = last_week_start_local.replace(hour=0, minute=0, second=0, microsecond=0)
+        end_local = last_week_end_local.replace(hour=23, minute=59, second=59, microsecond=999999)
+        
+        # Convert to UTC
+        start_date = start_local.astimezone(timezone.utc).replace(tzinfo=None)
+        end_date = end_local.astimezone(timezone.utc).replace(tzinfo=None)
+        
+    elif date_range_filter == 'this_month':
+        # Start of current month in user's local timezone
+        start_local = now_local.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
+        end_local = now_local
+        
+        # Convert to UTC
+        start_date = start_local.astimezone(timezone.utc).replace(tzinfo=None)
+        end_date = end_local.astimezone(timezone.utc).replace(tzinfo=None)
+        
+    elif date_range_filter == 'all':
+        start_date = None
+        end_date = None
+        
+    elif date_range_filter == 'custom':
+        # Parse custom date range
+        if start_date_filter:
+            try:
+                # Parse the date string
+                start_date_parsed = datetime.strptime(start_date_filter, '%Y-%m-%d')
+                
+                # Apply time if provided
+                if start_time_filter:
+                    try:
+                        hour, minute = map(int, start_time_filter.split(':'))
+                        start_date_parsed = start_date_parsed.replace(hour=hour, minute=minute, second=0, microsecond=0)
+                    except (ValueError, AttributeError):
+                        start_date_parsed = start_date_parsed.replace(hour=0, minute=0, second=0, microsecond=0)
+                else:
+                    start_date_parsed = start_date_parsed.replace(hour=0, minute=0, second=0, microsecond=0)
+                
+                # Treat the parsed date as being in the user's timezone
+                start_date_local = start_date_parsed.replace(tzinfo=tz)
+                start_date = start_date_local.astimezone(timezone.utc).replace(tzinfo=None)
+                
+            except ValueError:
+                pass
+        
+        if end_date_filter:
+            try:
+                # Parse the date string
+                end_date_parsed = datetime.strptime(end_date_filter, '%Y-%m-%d')
+                
+                # Apply time if provided
+                if end_time_filter:
+                    try:
+                        hour, minute = map(int, end_time_filter.split(':'))
+                        end_date_parsed = end_date_parsed.replace(hour=hour, minute=minute, second=59, microsecond=999999)
+                    except (ValueError, AttributeError):
+                        end_date_parsed = end_date_parsed.replace(hour=23, minute=59, second=59, microsecond=999999)
+                else:
+                    end_date_parsed = end_date_parsed.replace(hour=23, minute=59, second=59, microsecond=999999)
+                
+                # Treat the parsed date as being in the user's timezone
+                end_date_local = end_date_parsed.replace(tzinfo=tz)
+                end_date = end_date_local.astimezone(timezone.utc).replace(tzinfo=None)
+                
+            except ValueError:
+                pass
+    
+    return start_date, end_date
+
 @csrf.exempt
 @bp.route('/')
 def index():
@@ -1560,57 +1751,11 @@ def reports():
         page = request.args.get('page', 1, type=int)
         per_page = min(request.args.get('per_page', 50, type=int), 100)
         
-        # Calculate date range based on filter
-        now = datetime.utcnow()
-        start_date = None
-        end_date = None
-        
-        if date_range_filter == 'today':
-            start_date = now.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'yesterday':
-            yesterday = now - timedelta(days=1)
-            start_date = yesterday.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = yesterday.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_week':
-            # Start of current week (Monday)
-            start_date = now - timedelta(days=now.weekday())
-            start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'last_week':
-            # Start of last week (Monday)
-            last_week_end = now - timedelta(days=now.weekday() + 1)
-            last_week_start = last_week_end - timedelta(days=6)
-            start_date = last_week_start.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = last_week_end.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_month':
-            start_date = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'all':
-            start_date = None
-            end_date = None
-        elif date_range_filter == 'custom':
-            # Use custom date range
-            if start_date_filter:
-                try:
-                    start_date = datetime.strptime(start_date_filter, '%Y-%m-%d')
-                    if start_time_filter:
-                        hour, minute = map(int, start_time_filter.split(':'))
-                        start_date = start_date.replace(hour=hour, minute=minute, second=0, microsecond=0)
-                    else:
-                        start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-                except ValueError:
-                    pass
-            if end_date_filter:
-                try:
-                    end_date = datetime.strptime(end_date_filter, '%Y-%m-%d')
-                    if end_time_filter:
-                        hour, minute = map(int, end_time_filter.split(':'))
-                        end_date = end_date.replace(hour=hour, minute=minute, second=59, microsecond=999999)
-                    else:
-                        end_date = end_date.replace(hour=23, minute=59, second=59, microsecond=999999)
-                except ValueError:
-                    pass
+        # Calculate date range based on filter with timezone conversion
+        start_date, end_date = get_date_range_in_timezone(
+            date_range_filter, start_date_filter, end_date_filter,
+            start_time_filter, end_time_filter, timezone_filter
+        )
         
         # Base query
         if current_user.is_admin:
@@ -1922,54 +2067,11 @@ def export_reports(query, export_format):
         end_time_filter = request.args.get('end_time', '').strip()
         timezone_filter = request.args.get('timezone', 'auto').strip()
         
-        # Calculate date range based on filter
-        now = datetime.utcnow()
-        start_date = None
-        end_date = None
-        
-        if date_range_filter == 'today':
-            start_date = now.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'yesterday':
-            yesterday = now - timedelta(days=1)
-            start_date = yesterday.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = yesterday.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_week':
-            start_date = now - timedelta(days=now.weekday())
-            start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'last_week':
-            last_week_end = now - timedelta(days=now.weekday() + 1)
-            last_week_start = last_week_end - timedelta(days=6)
-            start_date = last_week_start.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = last_week_end.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_month':
-            start_date = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'all':
-            start_date = None
-            end_date = None
-        elif date_range_filter == 'custom':
-            if start_date_filter:
-                try:
-                    start_date = datetime.strptime(start_date_filter, '%Y-%m-%d')
-                    if start_time_filter:
-                        hour, minute = map(int, start_time_filter.split(':'))
-                        start_date = start_date.replace(hour=hour, minute=minute, second=0, microsecond=0)
-                    else:
-                        start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-                except ValueError:
-                    pass
-            if end_date_filter:
-                try:
-                    end_date = datetime.strptime(end_date_filter, '%Y-%m-%d')
-                    if end_time_filter:
-                        hour, minute = map(int, end_time_filter.split(':'))
-                        end_date = end_date.replace(hour=hour, minute=minute, second=59, microsecond=999999)
-                    else:
-                        end_date = end_date.replace(hour=23, minute=59, second=59, microsecond=999999)
-                except ValueError:
-                    pass
+        # Calculate date range based on filter with timezone conversion
+        start_date, end_date = get_date_range_in_timezone(
+            date_range_filter, start_date_filter, end_date_filter,
+            start_time_filter, end_time_filter, timezone_filter
+        )
         
         # Build query for MatchReport data (same as reports page)
         base_query = MatchReport.query
@@ -2418,54 +2520,11 @@ def export_match_report(client_id, match_id, export_format):
         end_time_filter = request.args.get('end_time', '').strip()
         timezone_filter = request.args.get('timezone', 'auto').strip()
         
-        # Calculate date range
-        now = datetime.utcnow()
-        start_date = None
-        end_date = None
-        
-        if date_range_filter == 'today':
-            start_date = now.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'yesterday':
-            yesterday = now - timedelta(days=1)
-            start_date = yesterday.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = yesterday.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_week':
-            start_date = now - timedelta(days=now.weekday())
-            start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'last_week':
-            last_week_end = now - timedelta(days=now.weekday() + 1)
-            last_week_start = last_week_end - timedelta(days=6)
-            start_date = last_week_start.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = last_week_end.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_month':
-            start_date = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'all':
-            start_date = None
-            end_date = None
-        elif date_range_filter == 'custom':
-            if start_date_filter:
-                try:
-                    start_date = datetime.strptime(start_date_filter, '%Y-%m-%d')
-                    if start_time_filter:
-                        hour, minute = map(int, start_time_filter.split(':'))
-                        start_date = start_date.replace(hour=hour, minute=minute, second=0, microsecond=0)
-                    else:
-                        start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-                except ValueError:
-                    pass
-            if end_date_filter:
-                try:
-                    end_date = datetime.strptime(end_date_filter, '%Y-%m-%d')
-                    if end_time_filter:
-                        hour, minute = map(int, end_time_filter.split(':'))
-                        end_date = end_date.replace(hour=hour, minute=minute, second=59, microsecond=999999)
-                    else:
-                        end_date = end_date.replace(hour=23, minute=59, second=59, microsecond=999999)
-                except ValueError:
-                    pass
+        # Calculate date range based on filter with timezone conversion
+        start_date, end_date = get_date_range_in_timezone(
+            date_range_filter, start_date_filter, end_date_filter,
+            start_time_filter, end_time_filter, timezone_filter
+        )
         
         # Check if user has access to this client
         if current_user.is_admin:
@@ -2649,54 +2708,11 @@ def export_client_report(client_id, export_format):
         end_time_filter = request.args.get('end_time', '').strip()
         timezone_filter = request.args.get('timezone', 'auto').strip()
         
-        # Calculate date range
-        now = datetime.utcnow()
-        start_date = None
-        end_date = None
-        
-        if date_range_filter == 'today':
-            start_date = now.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'yesterday':
-            yesterday = now - timedelta(days=1)
-            start_date = yesterday.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = yesterday.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_week':
-            start_date = now - timedelta(days=now.weekday())
-            start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'last_week':
-            last_week_end = now - timedelta(days=now.weekday() + 1)
-            last_week_start = last_week_end - timedelta(days=6)
-            start_date = last_week_start.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = last_week_end.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_month':
-            start_date = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'all':
-            start_date = None
-            end_date = None
-        elif date_range_filter == 'custom':
-            if start_date_filter:
-                try:
-                    start_date = datetime.strptime(start_date_filter, '%Y-%m-%d')
-                    if start_time_filter:
-                        hour, minute = map(int, start_time_filter.split(':'))
-                        start_date = start_date.replace(hour=hour, minute=minute, second=0, microsecond=0)
-                    else:
-                        start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-                except ValueError:
-                    pass
-            if end_date_filter:
-                try:
-                    end_date = datetime.strptime(end_date_filter, '%Y-%m-%d')
-                    if end_time_filter:
-                        hour, minute = map(int, end_time_filter.split(':'))
-                        end_date = end_date.replace(hour=hour, minute=minute, second=59, microsecond=999999)
-                    else:
-                        end_date = end_date.replace(hour=23, minute=59, second=59, microsecond=999999)
-                except ValueError:
-                    pass
+        # Calculate date range based on filter with timezone conversion
+        start_date, end_date = get_date_range_in_timezone(
+            date_range_filter, start_date_filter, end_date_filter,
+            start_time_filter, end_time_filter, timezone_filter
+        )
         
         # Check if user has access to this client
         if current_user.is_admin:
@@ -3099,54 +3115,11 @@ def client_report_detail(client_id):
         page = request.args.get('page', 1, type=int)
         per_page = min(request.args.get('per_page', 50, type=int), 100)
         
-        # Calculate date range
-        now = datetime.utcnow()
-        start_date = None
-        end_date = None
-        
-        if date_range_filter == 'today':
-            start_date = now.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'yesterday':
-            yesterday = now - timedelta(days=1)
-            start_date = yesterday.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = yesterday.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_week':
-            start_date = now - timedelta(days=now.weekday())
-            start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'last_week':
-            last_week_end = now - timedelta(days=now.weekday() + 1)
-            last_week_start = last_week_end - timedelta(days=6)
-            start_date = last_week_start.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = last_week_end.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_month':
-            start_date = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'all':
-            start_date = None
-            end_date = None
-        elif date_range_filter == 'custom':
-            if start_date_filter:
-                try:
-                    start_date = datetime.strptime(start_date_filter, '%Y-%m-%d')
-                    if start_time_filter:
-                        hour, minute = map(int, start_time_filter.split(':'))
-                        start_date = start_date.replace(hour=hour, minute=minute, second=0, microsecond=0)
-                    else:
-                        start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-                except ValueError:
-                    pass
-            if end_date_filter:
-                try:
-                    end_date = datetime.strptime(end_date_filter, '%Y-%m-%d')
-                    if end_time_filter:
-                        hour, minute = map(int, end_time_filter.split(':'))
-                        end_date = end_date.replace(hour=hour, minute=minute, second=59, microsecond=999999)
-                    else:
-                        end_date = end_date.replace(hour=23, minute=59, second=59, microsecond=999999)
-                except ValueError:
-                    pass
+        # Calculate date range based on filter with timezone conversion
+        start_date, end_date = get_date_range_in_timezone(
+            date_range_filter, start_date_filter, end_date_filter,
+            start_time_filter, end_time_filter, timezone_filter
+        )
         
         # Check if user has access to this client
         if current_user.is_admin:
@@ -3269,54 +3242,11 @@ def match_report_detail(client_id, match_id):
         page = request.args.get('page', 1, type=int)
         per_page = min(request.args.get('per_page', 50, type=int), 100)
         
-        # Calculate date range
-        now = datetime.utcnow()
-        start_date = None
-        end_date = None
-        
-        if date_range_filter == 'today':
-            start_date = now.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'yesterday':
-            yesterday = now - timedelta(days=1)
-            start_date = yesterday.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = yesterday.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_week':
-            start_date = now - timedelta(days=now.weekday())
-            start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'last_week':
-            last_week_end = now - timedelta(days=now.weekday() + 1)
-            last_week_start = last_week_end - timedelta(days=6)
-            start_date = last_week_start.replace(hour=0, minute=0, second=0, microsecond=0)
-            end_date = last_week_end.replace(hour=23, minute=59, second=59, microsecond=999999)
-        elif date_range_filter == 'this_month':
-            start_date = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
-            end_date = now
-        elif date_range_filter == 'all':
-            start_date = None
-            end_date = None
-        elif date_range_filter == 'custom':
-            if start_date_filter:
-                try:
-                    start_date = datetime.strptime(start_date_filter, '%Y-%m-%d')
-                    if start_time_filter:
-                        hour, minute = map(int, start_time_filter.split(':'))
-                        start_date = start_date.replace(hour=hour, minute=minute, second=0, microsecond=0)
-                    else:
-                        start_date = start_date.replace(hour=0, minute=0, second=0, microsecond=0)
-                except ValueError:
-                    pass
-            if end_date_filter:
-                try:
-                    end_date = datetime.strptime(end_date_filter, '%Y-%m-%d')
-                    if end_time_filter:
-                        hour, minute = map(int, end_time_filter.split(':'))
-                        end_date = end_date.replace(hour=hour, minute=minute, second=59, microsecond=999999)
-                    else:
-                        end_date = end_date.replace(hour=23, minute=59, second=59, microsecond=999999)
-                except ValueError:
-                    pass
+        # Calculate date range based on filter with timezone conversion
+        start_date, end_date = get_date_range_in_timezone(
+            date_range_filter, start_date_filter, end_date_filter,
+            start_time_filter, end_time_filter, timezone_filter
+        )
         
         # Check if user has access to this client
         if current_user.is_admin:

app/templates/main/_timezone_options.html

 <option value="auto" {% if filters.timezone == 'auto' or not filters.timezone %}selected{% endif %}>Auto (Browser Local)</option>
 <option value="UTC" {% if filters.timezone == 'UTC' %}selected{% endif %}>UTC</option>
+<optgroup label="UTC Offsets">
+    <option value="UTC-12" {% if filters.timezone == 'UTC-12' %}selected{% endif %}>UTC-12 (Baker Island)</option>
+    <option value="UTC-11" {% if filters.timezone == 'UTC-11' %}selected{% endif %}>UTC-11 (American Samoa)</option>
+    <option value="UTC-10" {% if filters.timezone == 'UTC-10' %}selected{% endif %}>UTC-10 (Hawaii)</option>
+    <option value="UTC-9" {% if filters.timezone == 'UTC-9' %}selected{% endif %}>UTC-9 (Alaska)</option>
+    <option value="UTC-8" {% if filters.timezone == 'UTC-8' %}selected{% endif %}>UTC-8 (Pacific Time)</option>
+    <option value="UTC-7" {% if filters.timezone == 'UTC-7' %}selected{% endif %}>UTC-7 (Mountain Time)</option>
+    <option value="UTC-6" {% if filters.timezone == 'UTC-6' %}selected{% endif %}>UTC-6 (Central Time)</option>
+    <option value="UTC-5" {% if filters.timezone == 'UTC-5' %}selected{% endif %}>UTC-5 (Eastern Time)</option>
+    <option value="UTC-4" {% if filters.timezone == 'UTC-4' %}selected{% endif %}>UTC-4 (Atlantic Time)</option>
+    <option value="UTC-3" {% if filters.timezone == 'UTC-3' %}selected{% endif %}>UTC-3 (Brazil, Argentina)</option>
+    <option value="UTC-2" {% if filters.timezone == 'UTC-2' %}selected{% endif %}>UTC-2 (Mid-Atlantic)</option>
+    <option value="UTC-1" {% if filters.timezone == 'UTC-1' %}selected{% endif %}>UTC-1 (Azores)</option>
+    <option value="UTC+0" {% if filters.timezone == 'UTC+0' %}selected{% endif %}>UTC+0 (GMT/UTC)</option>
+    <option value="UTC+1" {% if filters.timezone == 'UTC+1' %}selected{% endif %}>UTC+1 (Central European)</option>
+    <option value="UTC+2" {% if filters.timezone == 'UTC+2' %}selected{% endif %}>UTC+2 (Eastern European, South Africa)</option>
+    <option value="UTC+3" {% if filters.timezone == 'UTC+3' %}selected{% endif %}>UTC+3 (Moscow, East Africa)</option>
+    <option value="UTC+4" {% if filters.timezone == 'UTC+4' %}selected{% endif %}>UTC+4 (Gulf Standard)</option>
+    <option value="UTC+5" {% if filters.timezone == 'UTC+5' %}selected{% endif %}>UTC+5 (Pakistan)</option>
+    <option value="UTC+5:30" {% if filters.timezone == 'UTC+5:30' %}selected{% endif %}>UTC+5:30 (India)</option>
+    <option value="UTC+6" {% if filters.timezone == 'UTC+6' %}selected{% endif %}>UTC+6 (Bangladesh)</option>
+    <option value="UTC+7" {% if filters.timezone == 'UTC+7' %}selected{% endif %}>UTC+7 (Indochina)</option>
+    <option value="UTC+8" {% if filters.timezone == 'UTC+8' %}selected{% endif %}>UTC+8 (China, Singapore)</option>
+    <option value="UTC+9" {% if filters.timezone == 'UTC+9' %}selected{% endif %}>UTC+9 (Japan, Korea)</option>
+    <option value="UTC+10" {% if filters.timezone == 'UTC+10' %}selected{% endif %}>UTC+10 (Eastern Australia)</option>
+    <option value="UTC+11" {% if filters.timezone == 'UTC+11' %}selected{% endif %}>UTC+11 (Solomon Islands)</option>
+    <option value="UTC+12" {% if filters.timezone == 'UTC+12' %}selected{% endif %}>UTC+12 (New Zealand)</option>
+    <option value="UTC+13" {% if filters.timezone == 'UTC+13' %}selected{% endif %}>UTC+13 (Phoenix Islands)</option>
+    <option value="UTC+14" {% if filters.timezone == 'UTC+14' %}selected{% endif %}>UTC+14 (Line Islands)</option>
+</optgroup>
 <optgroup label="Africa">
     <option value="Africa/Abidjan" {% if filters.timezone == 'Africa/Abidjan' %}selected{% endif %}>Abidjan</option>
     <option value="Africa/Accra" {% if filters.timezone == 'Africa/Accra' %}selected{% endif %}>Accra</option>