That sounds like l10n gone seriously wrong -- maybe they literally wrote something like translation_helper(0) in that header which translates to Monday in $asian language and Sunday in English.
The bug looks like it occurs because the date picker aligns days/dates from 2017. February and March both begin on a Wednesday in the screenshot. I don't have iOS to test, but if this is the case, a flight for 1st Jan 2020 will incorrectly be aligned under Sunday instead of Wednesday.