Hi Jim,
How about this:
[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:
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…