@staticmethod
def delta_todate(num_yyyyddd):
    """
		To convert timedelta to date
		Parameters
		----------
		num_yyyyddd

		Returns
		-------
		datetime.datetime
		"""
    import datetime
    str_yyddd = str(num_yyyyddd)
    year = int(str_yyddd[:4])
    baseDate = datetime.date(year, 1, 1)
    days = int(str_yyddd[4:])
    return baseDate + datetime.timedelta(days=days)
