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sfttime(7)

sfttime - a hexadecimal time system based on fractional days

sfttime is an alternative representation of UTC time. For example, 2026-04-23 at 13:37 UTC (the start of sft day 5056) is written:

5056.000[sft]

Time is expressed as a hexadecimal count of days since the sfttime epoch, with a fractional component for sub-day precision. It is very regular, and timestamps are concise: a full timestamp with second-level precision fits in 12 characters. It is also a good fit for shell prompts and status lines, where only the sub-day part is needed — that requires only five characters, for example the start of the sfttime day (13:37 UTC) is .0000, and noon UTC is .EEC0.

A full sfttime timestamp looks like:

DDDD.FFF[sft]

Where:

DDDD

Hexadecimal count of days since the sfttime epoch. Grows by 1 each day.

.FFF

Fractional part of the current day in hexadecimal. Three digits give a resolution of 1/4096 of a day, approximately 21 seconds (one vergil). Four digits give a resolution of 1/65536 of a day, approximately 1.3 seconds (one tick).

[sft]

Optional suffix indicating the value is in sfttime. May be omitted in contexts where it is unambiguous.

The sub-day compact form omits the date entirely and is written as:

.F3C9

This is useful for timestamps where the date is known from context, such as log entries or status lines within a running session. Adding a fifth digit gives ~82ms precision (roughly 1/10 of a second), and a sixth digit gives millisecond-level precision (~5ms):

.F3C9A4

The sfttime epoch is 1970-01-01 13:37:00 UTC, which is 49020 seconds after the Unix epoch (1970-01-01 00:00:00 UTC). The choice of 13:37 is intentional.

Each power of 16 in the fractional part has a name:

**Unit**           **Duration**    **Example**   **Name**  
`[sft]0`           1 day           `1.0000[sft]` day  
`[sft]-1`          1.5 hours       `.1000[sft]`  major (one university lecture)  
`[sft]-2`          ~5.6 minutes    `.0100[sft]`  schinken  
`[sft]-3`          ~21 seconds     `.0010[sft]`  vergil  
`[sft]-4`          ~1.3 seconds    `.0001[sft]`  tick

Converting the current time:

$ sfttime
5055.F3C[sft]

A compact sub-day timestamp as used in status lines:

These timestamps represent the same moment expressed at different precisions:

**Timestamp**     **Precision**  
`5055[sft]`       day (24h)  
`5055.F[sft]`     major (1.5h)  
`5055.F3[sft]`    schinken (~5.6min)  
`5055.F3C[sft]`   vergil (~21s)  
`5055.F3C9[sft]`  tick (~1.3s)

To convert a sfttime timestamp to Unix time:

unix = hex_to_decimal(sfttime) * 86400 + 49020

To convert Unix time to sfttime:

sfttime = decimal_to_hex((unix - 49020) / 86400)

The name 'sft' is the clan name of a group of friends from Munich, Bavaria.

date(1)

Coordinated Universal Time (UTC)

https://en.wikipedia.org/wiki/Coordinated_Universal_Time

dot-time — a universal convention for conveying time

https://dotti.me/

sfttime was created in 3BBE.81[sft] (approximately 2013).