Random Dates for Test Data: Formats, Ranges and Pitfalls
Dates break software in surprising ways — leap years, month boundaries, time zones and ambiguous formats. Random dates across a wide range help you find those bugs early.
Choose the right format
- ISO 8601 (YYYY-MM-DD): unambiguous and sortable — best for databases and APIs.
- US (MM/DD/YYYY) and EU (DD/MM/YYYY): for display; never store these.
- Unix timestamp: seconds since 1970-01-01 UTC — ideal for APIs and logs.
Edge cases to include
- 29 February in leap years.
- 31st of months with 30 days (invalid inputs).
- Dates before 1970 for negative timestamps.
- Year boundaries and daylight-saving switches.
Other uses
Pick a random date for a surprise event, a “what happened on this day” history game or a random deadline for practice exams.
Pro tips
- Store in UTC, convert for display.
- Generate 100 dates across a 50-year range to stress-test sorting.
- Pair with the Time Generator for full timestamps.