Whilst waiting for my yearling badge to show up, I checked my profile and saw that I was listed as having been a member for a year, though when I hovered over that text, it showed me what date-time I joined which was (approximately) 1 hour and 19 minutes less than a year.
See the attached screengrab showing my system clock at GMT Daylight Time, or UTC+1. This means that I took the screengrab at 13:57:20 UTC.
I appreciate that I had been a member for a year to the nearest day, but if we are able to be more accurate than that, then shouldn't be be doing so? If nothing else, it would be easier to see when the yearling badge was due to be awarded.