hehe yeah

Your full file extension ends up being: MM.DD-text
but hopefully noone needs to parse it that way.

I tend to use YYYY-MM-DD_hh:mm:ss.zzz or YYYY-MM-DD_hh-mm-ss.zzz depending upon the requirement and just recently realised the problem with the . before the zzz.
Luckily I don't need to add the zzz quite often.