I just wanted to whole-heartedly agree here.
US time format needs to be changeable to locale-specific, configurable. And/or lock time-zone to (say) GMT/UTC w. no DST stuff, instead of the actual time zone the vCenter / ESXi's are located in, in case there are pieces of the overall environment that are in different time zones. (My nightmare would be have some hosts in (say) Arizona (no DST), some others in (say) New York, and the management servers in yet a different time zone. Now try to figure out when things really happened! ;^)
vCloud Director too. Same issue. Except individual Organizations might want to set their own, separate from vCloud system level.
This has not changed in 5.5, as far as i can tell, BTW. (That's why I'm surfing for an answer now...)
Maybe best would be to default to the setting of the underlying OS supporting vCenter / vCloud Dir / Whatever. But still allow date-time format to be over-ridden in vSphere and vCloud layers.
Personally, I'm a huge fan of ISO time/date format. Completely un-ambiguous. Sorts like a dream (which US system sucks horribly at.) Others will have their own opinions -- and should be allowed to set them!
VMware folks listening?
-- PeterB