timetags

A timetag is metadata that records the time associated with a data item or event. Timetags are used to order events, align data streams, and schedule actions in systems where events occur asynchronously or across devices.

Common forms include ISO 8601 date-time strings, Unix timestamps, and domain-specific formats. In multimedia protocols such as Open Sound Control (OSC), timetags are encoded as a 64-bit fixed-point value: the first 32 bits count seconds from the epoch and the last 32 bits count fractional seconds, based on the NTP epoch of 1900-01-01. Timetags may also be expressed in UTC or converted to local time for display.

Applications span networked sensors and logging systems that require precise event ordering; distributed applications that synchronize state; multimedia pipelines that schedule playback; and data analysis tasks that correlate measurements across devices.

Challenges include clock synchronization, precision, and drift. Tools such as the Network Time Protocol (NTP) and Precision Time Protocol (PTP) help align clocks, while leap seconds and time-zone conversions can complicate interpretation. Some timetags are relative to a system clock and must be translated to a common reference to enable cross-device analysis.

Related concepts include timestamps and time stamps in databases, as well as standards like ISO 8601 and Unix time.