from typing import Union
from typing import List
from datetime import datetime


def days_to_datetimes(days: Union[int, List[int]], offset: int = 2100) -> Union[datetime, List[datetime]]:
    """ Converts Julian days to datetimes given an offset 
    """
    days = [days] if isinstance(days, int) else days
    return [datetime.strptime(f'{day-offset}', '%j') for day in days]