I have always had a highly irregular period. My cycles have varied between three weeks and three months and everything in between.
During marathon training my cycles settled into being 36/37 days long. That is unusually predictable for me and I was happy about it.
Then today I broke that patten. I started bleeding on day 29. That's within a day of the dreaded normal cycle. Oh no. That would be kind of weird. And hilarious. And bad timing for Godmamam weekends.