[How To?] Make my forum use relative time

[UniqueMU]

Hello MyBB!
I wondered how I can make my forum use relative time in forumhome (for example: posted X minutes ago)
Now it's using Absolute (Today XX-XX)

I tried to read a bit about absolute and relative time and also using functions but it's not working (probably because of old version of MyBB)
My forum uses MyBB version 1.8.12
Thanks!

[Crazycat]

If I remember well, it's automatic:
"X minutes/hours ago" when the post is less than 12 hours,
"today H:i" when between 12 and 24h
"yesterday, H:i" when yesterday
absolute date for olders