cylc user guide: more advanced cycling info about cylc-doc

[benfitzpatrick]

We should also copy over something like the translation table at https://github.com/cylc/cylc/wiki/ISO-8601

[hjoliver]

Plus some examples relevant to climate modelling.

[oliver-sanders]

Another format to document:

• [[[<repetitions>/<date1>/<date2>]]]
  • e.g. [[[R5/^/^+P4D]]]

Another example to include:

• [[[<repetitions>/<duration>/(^|$)(+|-)<duration>]]]
  • e.g. [[[R/PT6H/^+PT30H]]]

See cylc/cylc-flow#1601

[matthewrmshin]

Note: time intervals and repeating intervals syntaxes are quite well explained by Wikipedia > ISO8601 > Time intervals.

[wxtim]

[[[<repetitions>/<date1>/<date2>]]] now covered:

https://cylc.github.io/cylc-doc/latest/html/user-guide/writing-workflows/scheduling.html#format-1-r-limit-datetime-datetime

[wxtim]

@oliver-sanders I'm not clear whether [[[<repetitions>/<duration>/(^|$)(+|-)<duration>]]] is format 4 in the documentation. If it is I think this is closable.

[oliver-sanders]

I think the last bit differs:

<repetitions>/<duration>/(^|$)(+|-)<duration>
(^|$)(+|-)<duration>

E.G.

^+PT1H

Vs:

R[limit?]/[interval]/[datetime]
[datetime]

E.G:

2000-01-01

[MetRonnie]

^+PT1H is still a datetime (ICP + 1 hour). There is an example in the docs:

R1//+P0D # Run once at the final cycle point

[oliver-sanders]

Yes, but it's a different (and non-iso8601) way of writing it which requires documentation.

[MetRonnie]

I think there is already ample explanation of ^+PT1H syntax? https://cylc.github.io/cylc-doc/nightly/html/user-guide/writing-workflows/scheduling.html#referencing-the-initial-and-final-cycle-points

[oliver-sanders]

That doesn't cover this particular example.

We could probably just do with a clarification of where this extension to ISO8601 is valid and slip a couple more examples in.