responseDateTimeRenderOption property

Determines how dates, times, and durations in the response should be rendered.

This is ignored if response_value_render_option is FORMATTED_VALUE. The default dateTime render option is SERIAL_NUMBER. Possible string values are:

• "SERIAL_NUMBER" : Instructs date, time, datetime, and duration fields to be output as doubles in "serial number" format, as popularized by Lotus 1-2-3. The whole number portion of the value (left of the decimal) counts the days since December 30th 1899. The fractional portion (right of the decimal) counts the time as a fraction of the day. For example, January 1st 1900 at noon would be 2.5, 2 because it's 2 days after December 30th 1899, and .5 because noon is half a day. February 1st 1900 at 3pm would be 33.625. This correctly treats the year 1900 as not a leap year.
• "FORMATTED_STRING" : Instructs date, time, datetime, and duration fields to be output as strings in their given number format (which depends on the spreadsheet locale).