from django.db.models import DecimalField, DurationField, Func class IntervalToSeconds(Func): function = "" template = """ EXTRACT(day from %(expressions)s) * 86400 + EXTRACT(hour from %(expressions)s) * 3600 + EXTRACT(minute from %(expressions)s) * 60 + EXTRACT(second from %(expressions)s) """ def __init__(self, expression, *, output_field=None, **extra): super().__init__( expression, output_field=output_field or DecimalField(), **extra ) class SecondsToInterval(Func): function = "NUMTODSINTERVAL" template = "%(function)s(%(expressions)s, 'SECOND')" def __init__(self, expression, *, output_field=None, **extra): super().__init__( expression, output_field=output_field or DurationField(), **extra )