Yes, I know this issue regularly comes up…
I submitted a post at 1:40 pm, my local time. I tried to edit it three minutes later, at 1:43. I got the pop-up window that told me I exceeded the five minute window for editing. I decided to check the time display at the bottom of the page. It said the time was 1:38 pm, or two minutes before I composed my post. And the timestamp on my post was 1:40 pm. If the clock were accurate, I never would have flagged the five minute limit.
I know I could ask a moderator to edit my post, but it wasn’t worth it, and I didn’t want to double post, either. I just though I’d vent.