Format a time according to format string fmt and using a optional time locale (= time-locale-en-isostd/time/locale/time-locale-en-iso: time-locale).

Letters (a to z) are always interpreted as a pattern where unknown letter patterns are ignored. Any literal text should be quote-escaped i.e. use "'GMT'ZZ" to display as "GMT-07:00" (in the PST time zone). Any characters other then an ascii letter are displayed as is.

Patterns of 2 letters are zero-padded on the left to always display as 2 digits. Allowed patterns:

• Y: the year as a number (without zero padding) (1970, 203)
• YY, `YYYY: the year in upto 4 digits (70, 1970, 0203). If the year is smaller than zero or larger than 9999, the year is displayed with 5 or more digits and preprended with an explicit sign (-00030, +10345).
• M, MM: the month. (1, 03). In case of an ISO week (cal-iso-week) or ISO month (cal-iso-month) calendar, the month is prefixed with W or M.
• MMM, MMMM: name of the month in the specified locale. (Jan, January)
• D, DD: the day of the month. (1, 08). If DD is used and this is an ISO week calendar (cal-iso-week) just one digit is used for the week day.
• DDD: the day of the year. (087)
• d: the ISO day of the week, 1 for Monday ending in 7 for Sunday.
• dd, ddd,dddd: the day of the week in the current locale. (We,Wed,Wednesday)
• h, hh: the hours using a 12-hour clock (with am/pm). (9, 09)
• H, HH: the hours using a 24-hour clock. (21, 09)
• m, mm: the minutes. (9, 09)
• s, ss: the whole seconds. (8, 08)
• a, aa: AM/PM designation. (a, am)
• A, AA: AM/PM designation in upper-case. (A, AM)
• f,…,fffffffff: upto 9 digits of a fraction of a second. Starts with a dot. (.320, .000)
• F,…,FFFFFFFFF: upto 9 digits of a fraction of a second. If not zero, starts with a dot. In contrast to the f patterns displays the minimal number of required digits (and is not right-padded with zeros). (.32)
• z: timezone offset in hours and minutes separated by a colon. Use +00:00 for UTC time. (+01:00)
• zz: timezone offset in hours and minutes without a separator. Use +0000 for UTC time. (-0700)
• Z: timezone offset in hours and minutes separated by a colon, use Z for UTC time.
• ZZ: timezone offset in hours and minutes separated by colon, use an empty string for UTC time.
• x: fractional seconds since min-time. (63610768799.429)
• YYYYYY: the year in ECMAscript 6 digits, prepended with the sign. (+002016,-000023,+000000)
• y: the absolute value of the year as a number (without zero padding). Useful when displaying Julian (cal-julian) negative years as 10 BC for example (e.g. "y E").
• C, CC: the short or long calendar name. (The short name is empty for the standard ISO calendars).
• E: the era name, for example CE for the Gregorian calendar.
• '...', "...": anything between quotes is displayed as is. ('M'M becomes M11 for November)

There are also various forms to display dates and times in a locale specific way. We give examples in English and Dutch. The lower-case l variants use short names for month- and day names.

• t: hours and minutes (3:21pm, 15:21)
• tt: hours, minutes, and seconds (3:21:01pm, 15:21:01)
• L, l: a date (09/29/2016, 29.09.2016) and (9/29/2016, 29.9.2016)
• LL, ll: date with month name (29 September 2016, 29 september 2016) and (29 Sep 2016, 29 sep 2016)
• LLL, lll: date with month name and time (29 September 2016 1:15pm, 29 september 2016 13:15)
• LLLL, llll: date with day name, month name, and time (Thursday, 29 September 2016 1:15pm) and (Thu, 29 Sep 2016 1:15pm)

After formatting, any left- or right white space is trimmed. This allows specifiers like "YYYY E C" that display correctly even if the era or calendar name is empty.

For example, to display a time in the standard Internet Message Format you can use now().formatstd/time/format/format: (t : time, fmt : string, locale : ? time-locale) -> string("ddd, D MMM Y HH:mm:ss zz") displayed as "Tue, 27 Sep 2016 06:36:55 -0700" for example.
A standard ISO string can be formatted as, "YYYY-MM-DD'T'HH:mm:ssFFFFFFFFFZ C".

Show time as a standard Internet Message Format date.
For example now().show-imfstd/time/format/show-imf: (t : time) -> string returns "Fri, 9 Oct 2016 11:57:45 -0700".

Show the time as a human readable string in the given locale (=time-locale-enstd/time/locale/time-locale-en: time-locale) For example now().show-en -> "Thu, 8 Oct 2016, 12:20pm". Uses the "llll" format string.

Show the date in human readable string in the given locale (=time-locale-enstd/time/locale/time-locale-en: time-locale). For example now().show-en-date -> "Thu, 8 Oct 2016". Uses the "ll" format string.

Show a time as a standard ISO string. Will use automatic week date or month date format for the cal-iso-week and cal-iso-month calendars.

Show a time as a standard ISO date. Will use automatic week date or month date format for the cal-iso-week and cal-iso-month calendars.