Dates have gone, d M Y showing instead

[Necroshen]

Since my upgrade I have noticed that all the thread dates have gone and have been replaced with "d M Y" the time stamp remains unaffected.
Is there anything that could be causing this? the site is not throwing any errors up. Would an out of date theme cause this issue?

vBulletin 5.1.4 Patch 3

Thanks

[Zachery]

What did you upgrade from?

[Necroshen]

5.1.2