Block time (out to in)

Model: in − out, adding 24 h when a clock-only in time is earlier than out

Accuracy: Exact to the minute (to the second with full timestamps)

When to use this: Use this for the time between two clock times when one of them may be on the other side of midnight: block time out to in, a flight time, a duty period, the gap between two logged events. It takes 2215, 22:15, 2215Z or a full timestamp, and reports the span in hours and minutes and in decimal hours.

Limitations: With clock times and no date, a span is read as less than 24 hours, because that is the only span a pair of bare clock times can describe; give full timestamps when it could be longer and the dates settle it instead. Equal clock times are a zero block, not a day. Mixing a zoned timestamp with a bare clock time is refused rather than guessed at. And this is arithmetic on the times you supply -- it does not know what 14 CFR 1.1 counts as flight time, only what you tell it the out and in were.

Worked example: Out 2215Z, in 0140Z. Source: Across-midnight arithmetic: 3 h 25 min. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.

Review: Not yet independently reviewed by a geodesist.

Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.

Status: version 1.0.0, core 0.1.0. See this tool in the verification report.

Checked against: 24 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.

Sources

• 14 CFR 1.1, General definitions (flight time), Federal Aviation Administration, Current as of the review date. "Flight time": from moving under its own power for flight until coming to rest after landing. Read free. Rules as of 2026-09-18.