What format should I use for the date/time inputs?

Use ISO 8601 format: YYYY-MM-DDTHH:MM:SS, for example 2026-07-21T09:00:00 for July 21, 2026 at 9:00:00 AM.

Can the start and end be on different days?

Yes, both inputs include the full date, so this works correctly across day, month, or even year boundaries.

Elapsed Time in Seconds Calculator

Calculate the precise number of seconds elapsed between a start and end date/time, useful for scientific timing, event logging, and any calculation requiring second-level precision rather than just days.

Inputs

Results

Total Elapsed Seconds: 5,025
Breakdown (H:M:S): 1h 23m 45s

Try an example

Formula

Elapsed Seconds = (End Date/Time − Start Date/Time) in seconds

Learn How This Works

Precision Time Calculations: Julian Days, Epochs, and Overtime

Julian Day Number, elapsed time in seconds, overtime hours, and days since the Unix epoch — four calculations built for exact time-and-date precision.

Frequently Asked Questions

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