Marine ETA Calculator
Add your voyage duration to an explicitly offset-qualified departure and show arrival in UTC and the original fixed offset.
A QUICK WALKTHROUGH
How to use this tool
- Enter departure with seconds and an explicit Z or numeric ±HH:mm offset; never an unqualified local time.
- Enter your nonnegative voyage duration in hours, then calculate.
- Calculate, then copy the report or download TXT.
Calculation
Arrival instant = departure instant + round(duration hours × 3,600,000) milliseconds. Original-offset arrival = that UTC instant displayed with the same numeric offset.
What the result covers
This is time arithmetic, not a voyage or safety prediction. It preserves a fixed offset and does not infer a named time zone or daylight-saving changes. Precision is milliseconds: input fractional seconds allow 1–3 digits, duration rounds to the nearest millisecond, and positive durations rounding to zero are rejected. Years are 0001–9999; leap seconds and the unknown offset −00:00 are unsupported.
Local processing
Inputs remain in your browser. Copy and TXT download contain your inputs, results, formula and scope note.
GOOD TO KNOW
Common questions
Why must I enter an offset?
An explicit Z or numeric offset identifies the instant without guessing your browser's local time zone. Calendar dates and time components are validated strictly.
Does the original-offset arrival account for daylight saving?
No. It uses the same fixed numeric offset throughout. Determine any destination time-zone or daylight-saving adjustment separately.