# `Feel.Analysis.Images.Temporal`
[🔗](https://github.com/FeeJai/BDM/blob/feel-v0.1.0/apps/feel/lib/feel/analysis/images/temporal.ex#L1)

The rules for the functions of `Feel.Builtin.Temporal` (`Feel.Analysis.Images`, D-161, step C): `day of week`,
`day of year`, `is`, `month of year`, `now`, `today` and `week of year`.

| Function | The type of the result |
| -------- | ---------------------- |
| `now()` | a date and time with a zone (the offset of the clock of the run), and never `null` |
| `today()` | a date, never `null` |
| `day of week(d)` | the names of the weekdays of the days of `d`: `"Monday"` to `"Sunday"` |
| `month of year(d)` | the names of the months of the days of `d` |
| `day of year(d)` | the numbers `[1..366]` that the days of `d` have |
| `week of year(d)` | the numbers `[1..53]` that the days of `d` have, as the weeks of ISO 8601 count them |
| `is(a, b)` | a boolean, never `null`; `false` if no value of one is the same as a value of the other |

The argument of the four calendar functions is a date or a date and time, whose fields are read as they are written (the
day of a date and time is that of its clock, D-109), or a list of one of them, which is the one (section 10.3.2.9.4). So
the type of the result is the one the **days** of the type of the argument have: the set of a date is a set of days
(D-109), and that of a date and time is a set of seconds on the lines of its clocks (`Feel.Type.Moment`), of which the days
are taken. A date in January 2021 is a day of week in the set of the days of that month, and a day of year in
`[1..31]`. The result is `null` only for an argument that is no date: `null`, a value of another kind, a list that does
not have exactly one item (a type does not say how many a list has), or a value of a type that is not known.

A range of days of a week has every weekday, and one of a year (366 days) every month; a shorter one is counted day by day.
The days of the year are those that each year the range touches has in it, and the weeks of a range of up to 3,000 days are
counted a week at a time. Past that the range has every day of the year (a leap year ends in the 366th within 2,921 days) and
every week (the weeks of a year that has 53 are not apart by more than 2,548 days), and both are tested against the run
for every day of ranges of every length up to that.

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*Consult [api-reference.md](api-reference.md) for complete listing*