Add cal::zoned_time type for timezone-aware daily scheduling

[ibrhmkoz]

Problem Statement

EdgeDB currently lacks a native type for representing time-of-day with timezone information, which is crucial for applications that need to schedule recurring daily events across different time zones. While datetime handles timezone-aware timestamps well, it includes date information which is unnecessary for daily recurring events. The existing cal::local_time lacks timezone context.

Use Case Example

• Sending daily reports to users in different time zones at their local 9 AM
• Scheduling daily system maintenance during off-peak hours for different regions
• Setting business hours for global operations
• Configuring notification preferences for users across time zones

Current Workarounds

1. Using datetime requires storing redundant date information
2. Using cal::local_time loses timezone context
3. Custom composite types combining cal::local_time and timezone strings require manual timezone handling

Proposed Solution

Add a new cal::zoned_time type that:

• Stores time-of-day with associated timezone information
• Supports both fixed offsets and IANA timezone names
• Handles DST transitions appropriately
• Integrates with existing temporal types and functions