Time Format Converter

Convert between 12-hour (AM/PM) and 24-hour time formats — batch, one per line.

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12-hour vs 24-hour time formats

The 12-hour format uses AM (ante meridiem) and PM (post meridiem). Noon is 12:00 PM and midnight is 12:00 AM — a common source of confusion. The 24-hour format (used in aviation, healthcare, military) runs 00:00–23:59: noon is 12:00, midnight is 00:00. This tool converts either direction and handles optional seconds (HH:MM:SS).

Built and maintained by Meet Shah · Last updated 19 July 2026

What this tool is used for

Converting a batch of 12-hour times from a schedule into the 24-hour form a system expects.
Reading a 24-hour timetable for an audience that uses AM and PM.
Normalising times pasted from several sources into one format before importing them.
Checking that a midnight or noon value is being interpreted correctly.
Converting shift times for a rota that spans midnight.

Frequently Asked Questions

How do 12- and 24-hour formats map at the boundaries?: Midnight is 00:00 and 12:00 AM; noon is 12:00 and 12:00 PM. That 12 AM/PM inversion is the single most error-prone point in the conversion, and it is why schedules often say "12 noon" explicitly.
Should AM and PM be capitalised?: Style guides differ — Chicago prefers lowercase with periods (a.m.), AP prefers lowercase, many technical contexts use capitals. It is a house-style choice, not a correctness one.
Why is ISO 8601 preferred for storage?: Because it is unambiguous, sorts lexicographically, and has no locale variants. 2024-03-15T14:30:00Z means one instant everywhere, where "3/15/24 2:30" means two different days depending on the reader.
Is 24:00 a valid time?: Yes, in ISO 8601 — it denotes end-of-day and equals 00:00 of the next day. Many parsers reject it, which is why it appears in specifications and rarely in practice.
How do I display duration versus time of day?: Differently. A time of day wraps at 24 hours; a duration does not, so a 30-hour task is legitimately "30:00" and formatting it as a clock time silently turns it into 6:00.
What does 12:00 AM actually mean?: Midnight, at the start of the day — which is why it is genuinely confusing and why timetables prefer 00:00 or say "midnight". 12:00 PM is noon, and the two are the most misread values in the format.
Does the format vary by locale?: Considerably. Most of the world writes 24-hour time by default, and the separator differs — a period in several European locales rather than a colon. Formatting through the locale rather than by hand is what gets this right.

Common errors and gotchas

Getting midnight wrong. 12 AM is 00:00 and 12 PM is noon, which is the single most common error here.
Assuming a leading zero is optional, when many systems require a fixed two-digit hour.
Losing the date when a time crosses midnight, so 00:30 belongs to the following day.
Mixing 24:00 and 00:00, which some standards allow as an end-of-day marker and others reject.
Converting without the time zone, which makes the result ambiguous the moment it is shared.