Function that tests if a point belongs to a interval modulo (i.e. an arc of circle)

is_in_arc.py

def belongs_to(t, a, b):
    """Return True if t belongs to real number interval [a, b], False otherwise."""
    return t >= a and t <= b

def is_in_arc(t, a, b, m=365):
    """Return True if t is in the interval [a, b] modulo m, False otherwise"""
    t, a, b = [x % m for x in (t, a, b)]    # convert all the values to their values modulo m
    if a < b: 
        return belongs_to(t, a, b)
    else: 
        return not belongs_to(t, b, a)

Useful for testing if a day-of-year is on a given day-of-year interval