# ISO8601 is a mystery

**URL:** <https://cylc.discourse.group/t/iso8601-is-a-mystery/305>\
**Category:** Cylc Support\
**Created:** [February 2, 2021, 6:15pm UTC](https://cylc.discourse.group/t/iso8601-is-a-mystery/305 "2021-02-02T18:15:34Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![hilary.j.oliver](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/hilary.j.oliver/32/4_2.png) [@hilary.j.oliver](https://cylc.discourse.group/u/hilary.j.oliver)\
**Post date:** [February 2, 2021, 10:31pm UTC](https://cylc.discourse.group/t/iso8601-is-a-mystery/305/2 "2021-02-02T22:31:10Z")

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Hi Jim,

How about this:

```ini
[cylc]
   cycle point format = "%Y-%m-%d"
[scheduling]  
   initial cycle point = "1958-02-01"
   final cycle point = "2021-02-01"
    # must start Feb 01, any year:
   initial cycle point constraints = "0201T00" 
   [[dependencies]]
       [[[R/P3M]]] # 3-month cycle 
          graph = foo # etc.

```

This generates:

```auto
foo.1958-02-01
foo.1958-05-01
foo.1958-08-01
foo.1958-11-01
foo.1959-02-01
foo.1959-05-01
foo.1959-08-01
foo.1959-11-01
foo.1960-02-01
foo.1960-05-01
foo.1960-08-01
foo.1960-11-01
etc.

```

And for the inter-cycle trigger, use (e.g.) `foo[-P1Y]` or `foo[-P3M]` depending on your requirements…

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