Python: convert 'days since 1990' to datetime object

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长情又很酷
长情又很酷 2021-02-20 02:04

I have a time series that I have pulled from a netCDF file and I\'m trying to convert them to a datetime format. The format of the time series is in \'days since 1990-01-01 00:0

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  •  太阳男子
    2021-02-20 02:31

    The datetime module's timedelta is probably what you're looking for.

    For example:

    from datetime import date, timedelta
    
    days = 9465                 # This may work for floats in general, but using integers
                                #   is more precise (e.g. days = int(9465.0))
    
    start = date(1990,1,1)      # This is the "days since" part
    
    delta = timedelta(days)     # Create a time delta object from the number of days
    
    offset = start + delta      # Add the specified number of days to 1990
    
    print(offset)               # >>>  2015-12-01
    print(type(offset))         # >>>  
    

    You can then use and/or manipulate the offset object, or convert it to a string representation however you see fit.

    You can use the same format as for this date object as you do for your time_datetime:

    print(offset.strftime('%Y-%m-%d %H:%M:%S'))
    

    Output:

    2015-12-01 00:00:00
    

    Instead of using a date object, you could use a datetime object instead if, for example, you were later going to add hours/minutes/seconds/timezone offsets to it.

    The code would stay the same as above with the exception of two lines:

    # Here, you're importing datetime instead of date
    from datetime import datetime, timedelta
    
    # Here, you're creating a datetime object instead of a date object
    start = datetime(1990,1,1)   # This is the "days since" part
    

    Note: Although you don't state it, but the other answer suggests you might be looking for timezone aware datetimes. If that's the case, dateutil is the way to go in Python 2 as the other answer suggests. In Python 3, you'd want to use the datetime module's tzinfo.

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