def atom(ch):
    """atom(ch) - ascii-to-multiplyer - converts ascii char to a time multiplyer.
       eg: s=seconds, m=minutes, h=hours, d=days, w=weeks, c=calendar=months, y=years"""
    if ch == 's' or ch == 'S':
        mult = 1
    elif ch == 'm' or ch == 'M':
        mult = 60
    elif ch == 'h' or ch == 'H':
        mult = 60 * 60
    elif ch == 'd' or ch == 'D':
        mult = 60 * 60 * 24
    elif ch == 'w' or ch == 'W':
        mult = 60 * 60 * 24 * 7
    elif ch == 'c' or ch == 'C':
        mult = 60 * 60 * 24 * 30
    elif ch == 'y' or ch == 'Y':
        mult = 60 * 60 * 24 * 365
    else:
        mult = None
    return mult
