Second-Sync

Precise server time, at a glance.

Second-Sync is a time synchronization tool for moments where one second matters, such as course registration and ticketing. It multi-samples the HTTP Date of your chosen site and aligns the difference from the server clock down to milliseconds. Drift tracking maintains accuracy over time, while the PiP timer lets you watch live server time even when using other apps.

Key features
- Precise synchronization: collects HTTP Date in parallel at least 30 times, then calculates the offset after RTT compensation, outlier removal, and EMA smoothing.
- Drift estimation: runs linear regression on measured samples to track the slope of the device clock and maintain accuracy as time passes.
- PiP timer: opens a Picture in Picture timer as a companion app, so you can monitor the server clock live while using a browser or other apps.
- Example site shortcuts: quick buttons to load course registration pages for major Korean universities and ticket booking sites.
- Multilingual support: supports Korean, English, Japanese, and Simplified Chinese, with a separate in-app language setting.

Recommended for
- Anyone who wants exact server time in situations where it is critical, such as registration, ticketing, or reservations.
- Anyone who wants to keep accurate server time visible on iPhone or iPad while booking on the go.

Notes
- Synchronization may fail on sites that do not support the HTTP Date header. If so, enter another target server or use the example sites in the app.
- Picture in Picture works only on supported devices running iOS 15 or later, including iPadOS.
- Sync your server time with Second-Sync now. One button gives you stable synchronization and a PiP timer, so you do not miss the important moment!