I just had the same problem, my locale was set to en_NZ. it has been working for a few weeks, and suddenly i was getting these php errors.
changing to US fixed it on the public site, but the admin didn't work at all.
after a while of frustration, I tried using firefox instead of chrome. and it worked prefectly.
i shut down chrome, reopened- and, yes, all working
so if you experience this problem and it's just started, try closing and reopening....