About

Time representation varies across industries, countries, and protocols. Aviation and military operations use zero-padded 24-hour notation. Medical records require ISO 8601 (HH:MM:SS). Legal documents in the US default to 12-hour with AM/PM. Financial timestamps log Unix epoch seconds. Confusing 12:00 AM with 12:00 PM has caused missed medication doses, flight errors, and contractual disputes. This tool converts a single clock time input into 9 standardized formats simultaneously, including French Revolutionary decimal time and Swatch Internet Time (@beats). It applies exact arithmetic rather than locale-dependent library calls, so edge cases like midnight (00:00 vs 12:00 AM) and noon are handled correctly.

Limitation: spoken English output covers standard American English phrasing. Decimal and Swatch conversions assume the input represents a time-of-day within a single 24-hour period. The Unix timestamp is computed relative to today's date in your local timezone.

Formulas

The 12-hour to 24-hour conversion follows this piecewise rule:

{

h₂₄ = 0 if h₁₂ = 12 and AMh₂₄ = h₁₂ if AM and h₁₂ ≠ 12h₂₄ = h₁₂ if PM and h₁₂ = 12h₂₄ = h₁₂ + 12 if PM and h₁₂ ≠ 12

Swatch Internet Time (@beats) is computed from Biel Mean Time (UTC+1):

@B = s_BMT86.4

where s_BMT is seconds since midnight in UTC+1. The result is always in the range [0, 1000).

French Revolutionary decimal time maps the standard day:

h_dec = S_total8640 , m_dec = S_total mod 864086.4

where S_total = h × 3600 + m × 60 + s is the total standard seconds since midnight. One decimal hour = 8640 standard seconds. One decimal minute = 86.4 standard seconds.

Reference Data

Format	Example	Standard / Usage	Midnight	Noon
12-Hour	2:30:00 PM	US civil, Commonwealth casual	12:00:00 AM	12:00:00 PM
24-Hour	14:30:00	ISO 8601, EU civil, rail	00:00:00	12:00:00
Military	1430	NATO, US/UK armed forces	0000	1200
ISO 8601	T14:30:00	Data interchange, APIs, logs	T00:00:00	T12:00:00
Spoken English	two thirty PM	Verbal communication, TTS	twelve o'clock AM	twelve o'clock PM
Unix Timestamp	1718889000	POSIX, databases, APIs	Varies by date	Varies by date
Decimal (French Rev.)	6.0417	French Republican Calendar	0.0000	5.0000
Swatch Internet Time	@646.53	Swatch AG (BMT, UTC+1)	@0 (at UTC+1)	@500
Total Seconds	52200	Programming, elapsed time	0	43200
Percentage of Day	60.42%	Scheduling analytics	0.00%	50.00%
Decimal time divides the day into 10 hours of 100 minutes of 100 seconds each
Swatch beats divide the day into 1000 beats from Biel Mean Time (UTC+1)

Frequently Asked Questions

The 12-hour convention defines AM (ante meridiem) as before noon and PM (post meridiem) as after noon. Since 12:00 is exactly the meridian transition point, the convention assigns 12:00 AM to midnight (start of day) and 12:00 PM to noon. This is a source of frequent errors. ISO 8601 avoids this ambiguity entirely by using 00:00 for midnight and 12:00 for noon in 24-hour notation.

Swatch Internet Time eliminates time zones entirely. It uses a single reference: Biel Mean Time (BMT), which equals UTC+1. The day is divided into 1000 beats. @000 corresponds to midnight BMT. This means the same @beat value is identical worldwide at any given instant. One beat equals 86.4 standard seconds, or 1 minute 26.4 seconds.

French Revolutionary decimal time was mandated in France from 1794 to 1800. It divides the day into 10 decimal hours, each containing 100 decimal minutes of 100 decimal seconds. One decimal second equals 0.864 standard seconds. It is no longer in official use anywhere, but it remains useful in computational contexts where base-10 time simplifies calculations, and it appears in historical research.

A Unix timestamp represents the number of seconds elapsed since January 1, 1970 00:00:00 UTC (the Unix epoch). A clock time like 14:30 has no date component, so this tool combines the input time with today's date in your local timezone to compute a concrete timestamp. The same clock time on a different date produces a different Unix timestamp. The offset is exactly 86400 per day.

Military time omits the colon separator. 14:30 in 24-hour format becomes 1430 in military format. Hours below 10 use a leading zero (0900 instead of 9:00). Midnight is 0000 and is sometimes spoken as "zero hundred hours." The format is used in NATO operations, emergency services, and aviation to prevent AM/PM confusion in critical communications.

The input fields clamp values to valid ranges: hours 1-12 (12h mode) or 0-23 (24h mode), minutes 0-59, seconds 0-59. If you type 99 into the minutes field, it is clamped to 59. The value 24:00:00 is a valid ISO 8601 representation for midnight ending a day, but since this tool formats a point-in-time (not a duration), it normalizes to 00:00:00.