The problem:
php's strftime uses locale information and %p (ante-meridian, post-meridian modifier) is setted to null in many locales,
which is partially correct because it is not used on that locale.

If you have a multilingual environment you still have one locale, in my case portuguese and we use 24h format, however
there are pages written in english where the time representation uses %p, thus the effect is that time is represented in a
12-hour format and with a blank for %p.

Solution:
Set a default if %p is empty.