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Category Time

Enter time (e.g., 7:00 PM)

Format: 1:00 AM – 12:59 PM

Enter times (one per line) One time per line. Format: hh:mm AM/PM

Presets:

Result

Batch Results

#	Input	24-Hour Output	Status

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About

Incorrect time format conversion causes silent data corruption in databases, scheduling conflicts in APIs, and broken timestamp comparisons. The 12-hour clock with its AM/PM designator is ambiguous at the boundaries: 12:00 AM is midnight (00:00), not noon. Confusing these two values shifts records by exactly 12 hours. This converter parses input in hh:mm AM|PM format and outputs ISO-compliant HH:MM:SS 24-hour time. It validates hour range 1 - 12, minute range 00 - 59, and rejects malformed input rather than guessing intent.

Batch mode processes multiple lines simultaneously. The tool handles edge cases that trip up naive implementations: 12:30 PM stays 12:30:00, while 12:30 AM becomes 00:30:00. Limitation: this tool does not parse seconds or timezone offsets. It assumes local wall-clock time input.

Formulas

The conversion from 12-hour to 24-hour format applies a piecewise function on the hour component h based on the meridiem designator m:

H₂₄ = {

0 if m = AM ∧ h = 12h if m = AM ∧ h ≠ 1212 if m = PM ∧ h = 12h + 12 if m = PM ∧ h ≠ 12

Where h is the input hour (1 - 12), m is the meridiem (AM or PM), and H₂₄ is the resulting hour in 24-hour notation (0 - 23). The minute component passes through unchanged. The output is zero-padded to two digits and seconds are appended as 00.

Input validation regex pattern: ^(\d{1,2}):(\d{2})\s*(AM|PM)$ with case-insensitive flag. Hour validated against range [1, 12], minutes against [0, 59].

Reference Data

12-Hour Input	24-Hour Output	Common Name	Note
12:00 AM	00:00:00	Midnight	Start of day
12:30 AM	00:30:00	After midnight	Hour resets to 0
1:00 AM	01:00:00	Early morning	Direct mapping
6:00 AM	06:00:00	Morning	Direct mapping
11:59 AM	11:59:00	Late morning	Last AM minute
12:00 PM	12:00:00	Noon	Hour stays 12
12:30 PM	12:30:00	After noon	Hour stays 12
1:00 PM	13:00:00	Afternoon	1 + 12
5:00 PM	17:00:00	Evening	5 + 12
6:45 PM	18:45:00	Early evening	6 + 12
9:00 PM	21:00:00	Night	9 + 12
11:59 PM	23:59:00	Late night	Last minute of day
0:00 AM	Invalid - hour must be 1 - 12
13:00 PM	Invalid - hour exceeds 12
7:60 AM	Invalid - minutes exceed 59

Frequently Asked Questions

In the 24-hour system, midnight marks the start of a new day at hour 00. The 12-hour convention assigns 12:xx AM to the midnight hour and 12:xx PM to the noon hour. This is a source of frequent errors. The conversion rule sets H₂₄ = 0 when h = 12 and the designator is AM.

Yes. The parser treats the whitespace between minutes and the meridiem as optional. Both 7:00 PM and 7:00PM are accepted. However, the meridiem designator itself (AM or PM) is required. Input like 7:00 alone is rejected as ambiguous.

The 12-hour clock uses hours 1 through 12 only. An hour of 0 or any value above 12 is invalid in this notation and the converter returns an error. If you already have a 24-hour value like 13:00, no conversion is needed.

Yes. Enter one time per line in the input field and enable batch mode. Each line is parsed and converted independently. Invalid lines are flagged individually without affecting valid entries in the same batch.

ISO 8601 specifies time as HH:MM:SS in 24-hour notation with zero-padded values. This converter outputs exactly that format. It does not append timezone offset (e.g., +05:00 or Z) because the input carries no timezone information. Append the offset manually if needed for full ISO 8601 compliance.

12:00 PM is noon (12:00:00 in 24-hour time). 12:00 AM is midnight (00:00:00). This is the single most common confusion point in time conversion and the primary cause of 12-hour scheduling bugs.