In The Netherlands it is possible that you get paid extra (above your hourly wage) if you have 'irregular' working hours, e.g. you work at uncommon times, like Saturdays, Sundays, national holidays etc.
This is called onregelmatigheidstoeslag, which Google translates as irregularity allowance. Its official abbreviation is ORT.
Is irregularity allowance the correct English translation*, and what would its abbreviation be?
(If there's any difference, we prefer American English in our software translations).
* I do find that term online, but it's on Dutch sites, so I don't consider that decisive.