HHMMSS

HHMMSS is a compact time-of-day notation in which a six-digit string encodes hours, minutes, and seconds in the order hours, minutes, seconds. The standard convention uses a 24-hour clock, with hours from 00 to 23 and minutes and seconds from 00 to 59. This format is often chosen when a colon-free, fixed-width representation is desirable, such as in filenames, log entries, database timestamp fields, or other machine-readable records.

In practice, HHMMSS is typically stored as a string to preserve leading zeros, though it can be treated as an integer in some calculations. For example, the string "131045" represents 13:10:45. The value "000001" corresponds to 00:00:01. Because HHMMSS encodes only time of day, it does not include a date or time zone, making it ambiguous across days or zones unless paired with additional information.

Variants and related formats include representations with separators, such as HH:MM:SS, which are more human-friendly and explicit about boundaries between hours, minutes, and seconds. Some systems also support fractional seconds, written as HHMMSS.fraction or HH:MM:SS.fraction. While HHMMSS is common in computing contexts, many standards prefer ISO 8601-style time representations for clarity and interoperability, especially when dates, time zones, or durations are involved.

See also: time notation, 24-hour clock, ISO 8601, timestamp.