dies non
Concise Oxford English Dictionary © 2008 Oxford University Press:
dies non /ˌdiːeɪz ˈnɒn/
▶noun (pl. same) a day on which no legal business can be done, or which does not count for legal purposes.
– origin L., short for dies non juridicus ‘non-judicial day’.
'dies non' also found in these Oxford entries:

