Converting excel date serial to date in postgres - excel

Question

So I've got a large mass of excel files that aren't formatted properly and because of this their dates aren't being read in as dates, but as the date serial they use (i think the number of days since 1900-1-1?). Ex: 41917.0054050926 is really 10/5/2014 12:07:47 AM.
All I need is the actual date, not the time. I know I can get the year by doing 41917/365.25, rounding and adding this to 1900, but i'm not sure how to get the day and the month. Is there anything built into postgres to handle this? If not, does anyone know an arithmetic way of finding the day and year?
Thanks!

Answer 1

I just had this issue and wrote a plpgsql function to handle it. Note that it will work on whole numbers only meaning it will only do dates, not date and time. Someone else can feel free to expand it.
CREATE OR REPLACE FUNCTION To_Timestamp_From_Excel (ExcelDate integer)
RETURNS timestamp without time zone AS $$
BEGIN
IF ExcelDate > 59 THEN
ExcelDate = ExcelDate - 1;
END IF;
RETURN date '1899-12-31' + ExcelDate;
END;
$$ LANGUAGE plpgsql;
You would need to call it like this if you have date and time encoded or if your field type is text:
UPDATE myTable set MyDateField = to_Timestamp_From_Excel(MyDateField::integer)

Answer 2

With data in A1, in B1 enter:
=ROUND(A1,0)+1
and format B1 as mm/dd/yyyy
For example:

Answer 3

Its a little bit messy and not 100% accurate, but I can do this in a custom PG procedure:
41917.0054050926/365.25 gets the year
41917.0054050926%365.25 gets the day of the year
I can then add the day of the year as an interval to the last day of the previous year.

Answer 4

I use an instruction like that:
select timestamp '1899/12/30' + interval '43404 day 43200'
to obtain '2018/10/30 12:00:00'
In Excel this date is 43404.5, then i have integer part before "day" inside interval, and fraction multiplied by 86400 (seconds per day).

Answer 5

Try this
CREATE OR REPLACE FUNCTION cdate(rhs anyelement) RETURNS timestamp without time zone AS
$BODY$
DECLARE retval timestamp without time zone;
BEGIN
IF pg_typeof($1)=ANY ('{int2,int,int8,real,float8,numeric}'::regtype[]) THEN
retval:=DATE_TRUNC('second',DATE('1899-12-30')+$1*INTERVAL '1 day');
ELSE
IF pg_typeof($1)=ANY ('{timestamp,date}'::regtype[]) THEN
retval:=$1::timestamp without time zone;
END IF;
END IF;
RETURN retval;
END;
$BODY$
LANGUAGE plpgsql IMMUTABLE STRICT;

Answer 6

Without creating the function, you can try:
Postgresql convert sql date to excel serialized date:
date_part('day', here_your_date - '1900-01-01'::date)+2 AS excel_serialized_date
Excel serialized to Postgresql date:
-- for e.g.: excel_serialized_date = 44492
(to_date('1900-01-01','YYYY-MM-DD') + excel_serialized_date::integer)-2 as exceldate_to_postgresqldate,
/* https://learn.microsoft.com/en-us/office/troubleshoot/excel/wrongly-assumes-1900-is-leap-year
therefore -2 is needed */
In the Excel quick verification by the formula:
=Text(44492,"YYYY-MM-DD")