Timestamp and Date Generation Utilities for Developers
Timestamps are the backbone of logging, scheduling, and data synchronization. This guide covers Unix timestamps, ISO 8601, and generating dates for testing various scenarios.
Key Takeaways
- Seconds since January 1, 1970 00:00:00 UTC (the Unix epoch).
- Generate dates relative to 'now' for test scenarios:
- Generate timestamps with various offsets to test timezone handling:
- Always store timestamps in UTC and convert to local time only at the display layer.
Unix Timestamp Converter
Convert between Unix timestamps and human-readable dates
Timestamp Formats
| Format | Example | Use Case |
|---|---|---|
| Unix (seconds) | 1741564800 | APIs, databases |
| Unix (milliseconds) | 1741564800000 | JavaScript, Java |
| ISO 8601 | 2026-03-10T00:00:00Z | JSON, XML, display |
| RFC 2822 | Tue, 10 Mar 2026 00:00:00 +0000 | Email headers |
| Human readable | March 10, 2026 | UI display |
Unix Timestamp
Seconds since January 1, 1970 00:00:00 UTC (the Unix epoch). Simple, timezone-agnostic, and easy to compute durations by subtracting.
2038 problem: 32-bit Unix timestamps overflow on January 19, 2038. Most modern systems use 64-bit timestamps, but check legacy systems.
Generating Test Dates
Relative Dates
Generate dates relative to 'now' for test scenarios:
- 1 hour ago (recently created)
- 30 days ago (monthly billing cycle)
- 366 days ago (leap year boundary)
- 5 years in the future (subscription expiry)
Boundary Dates
| Scenario | Test Date | Why |
|---|---|---|
| Leap year | 2028-02-29 | Feb 29 exists |
| Non-leap year | 2027-02-28 | Feb 29 does not exist |
| Century leap year | 2000-02-29 | Divisible by 400, so it IS leap |
| Non-century leap | 1900-02-28 | Divisible by 100 but not 400, NOT leap |
| DST spring forward | 2026-03-08 02:30 EST | This time does not exist |
| DST fall back | 2026-11-01 01:30 EST | This time occurs twice |
| Year boundary | 2025-12-31 23:59:59 | Midnight rollover |
Timezone Generation
Generate timestamps with various offsets to test timezone handling:
- UTC (Z or +00:00)
- Positive offsets: +05:30 (India), +09:00 (Japan)
- Negative offsets: -05:00 (EST), -08:00 (PST)
- Half-hour offsets: +05:45 (Nepal), +09:30 (Australia Central)
Best Practice
Always store timestamps in UTC and convert to local time only at the display layer. This prevents ambiguity and makes timestamp comparison trivial.