Analyzing program logs, server maintenance schedules, API expiration settings—the daily life of a developer is full of “time” handling. However, failing to consider timezones or confusing seconds with milliseconds can sometimes trigger serious issues.
Timezones: The Wall Between UTC and Local Time
In global services and cloud environments, it’s common to operate server clocks (system clocks) in Coordinated Universal Time (UTC). On the other hand, the display or reports for local users might use a local standard time (like JST in Japan).
- UTC (Coordinated Universal Time): The common global reference time.
- Local Time (e.g., JST): For example, JST is 9 hours ahead of UTC (UTC+9).
If a log records 2026-02-16 06:00:00 UTC, that is 2026-02-16 15:00:00 JST in Japan. If you don’t correctly grasp this “9-hour offset,” it can lead to mistakes in identifying the time of a failure or cause batch processes to run twice—or not at all.
Time Units: From Milliseconds to Weeks
Various time units are used for API and database configuration values:
- Cache TTL: Usually in seconds.
- Java/JavaScript Timestamps: In milliseconds.
- Distributed System Timeouts: From microseconds to milliseconds.
Mistakes like, “I thought this setting was for 1 hour (3,600 seconds) so I put 3600, but it was actually in milliseconds, so the expiration happened in a few seconds,” are classic occurrences on a development floor.
For Precise Time Operations
In development, we recommend using tools that can calculate reliably rather than relying on mental math or manual calculation.
- Timezone Converter: Instantly convert between UTC and JST. You can also convert between any two timezones.
- Time Units Converter: Cross-convert major time units all at once, from milliseconds to several weeks ahead.
Aim for safer and more reliable system development and operation by zeroing out time-related calculation errors.