Pick up standard strat ages from Wikipedia?

[kwinkunks]

From here https://en.wikipedia.org/wiki/Template:Geologic_Ages_Inline or https://en.wikipedia.org/wiki/Template:Period_start (currently being merged)

Probably closest thing to an online API.

[Gert-JanPeeters]

There is an online API maintained by PaleoBioDatabase:

https://paleobiodb.org/data1.2/intervals_doc.html https://paleobiodb.org/data1.2/intervals/list.txt?scale=1

I hope that's what you're searching for...

Btw, not sure if this repo is still active but if so I'm interested in contributing to it...

[kwinkunks]

I think Macrostrat would be a good source too. Need to compare options before deciding.