Excel date to Unix timestamp

Question

Does anyone know how to convert an Excel date to a correct Unix timestamp?

Answer 1

I had an old Excel database with "human-readable" dates, like 2010.03.28 20:12:30 Theese dates were in UTC+1 (CET) and needed to convert it to epoch time.

I used the =(A4-DATE(1970;1;1))*86400-3600 formula to convert the dates to epoch time from the A column to B column values. Check your timezone offset and make a math with it. 1 hour is 3600 seconds.

The only thing why i write here an anwser, you can see that this topic is more than 5 years old is that i use the new Excel versions and also red posts in this topic, but they're incorrect. The DATE(1970;1;1). Here the 1970 and the January needs to be separated with ; and not with ,

If you're also experiencing this issue, hope it helps you. Have a nice day :)

Answer 2

Non of these worked for me... when I converted the timestamp back it's 4 years off.

This worked perfectly: =(A2-DATE(1970,1,1))*86400

Credit goes to: Filip Czaja http://fczaja.blogspot.ca

Original Post: http://fczaja.blogspot.ca/2011/06/convert-excel-date-into-timestamp.html

Answer 3

You're apparently off by one day, exactly 86400 seconds. Use the number 2209161600 Not the number 2209075200 If you Google the two numbers, you'll find support for the above. I tried your formula but was always coming up 1 day different from my server. It's not obvious from the unix timestamp unless you think in unix instead of human time ;-) but if you double check then you'll see this might be correct.

Answer 4

Here is a mapping for reference, assuming UTC for spreadsheet systems like Microsoft Excel:

                         Unix  Excel Mac    Excel    Human Date  Human Time
Excel Epoch       -2209075200      -1462        0    1900/01/00* 00:00:00 (local)
Excel ≤ 2011 Mac† -2082758400          0     1462    1904/12/31  00:00:00 (local)
Unix Epoch                  0      24107    25569    1970/01/01  00:00:00 UTC
Example Below      1234567890      38395.6  39857.6  2009/02/13  23:31:30 UTC
Signed Int Max     2147483648      51886    50424    2038/01/19  03:14:08 UTC

One Second                  1       0.0000115740…             —  00:00:01
One Hour                 3600       0.0416666666…             ―  01:00:00
One Day                 86400          1        1             ―  24:00:00

_{*  “Jan Zero, 1900” is 1899/12/31; see the Bug section below. † Excel 2011 for Mac (and older) use the 1904 date system.}

 

As I often use awk to process CSV and space-delimited content, I developed a way to convert UNIX epoch to timezone/DST-appropriate Excel date format:

echo 1234567890 |awk '{ 
  # tries GNU date, tries BSD date on failure
  cmd = sprintf("date -d@%d +%%z 2>/dev/null || date -jf %%s %d +%%z", $1, $1)
  cmd |getline tz                                # read in time-specific offset
  hours = substr(tz, 2, 2) + substr(tz, 4) / 60  # hours + minutes (hi, India)
  if (tz ~ /^-/) hours *= -1                     # offset direction (east/west)
  excel = $1/86400 + hours/24 + 25569            # as days, plus offset
  printf "%.9f\n", excel
}'

I used echo for this example, but you can pipe a file where the first column (for the first cell in .csv format, call it as awk -F,) is a UNIX epoch. Alter $1 to represent your desired column/cell number or use a variable instead.

This makes a system call to date. If you will reliably have the GNU version, you can remove the 2>/dev/null || date … +%%z and the second , $1. Given how common GNU is, I wouldn't recommend assuming BSD's version.

The getline reads the time zone offset outputted by date +%z into tz, which is then translated into hours. The format will be like -0700 (PDT) or +0530 (IST), so the first substring extracted is 07 or 05, the second is 00 or 30 (then divided by 60 to be expressed in hours), and the third use of tz sees whether our offset is negative and alters hours if needed.

The formula given in all of the other answers on this page is used to set excel, with the addition of the daylight-savings-aware time zone adjustment as hours/24.

If you're on an older version of Excel for Mac, you'll need to use 24107 in place of 25569 (see the mapping above).

To convert any arbitrary non-epoch time to Excel-friendly times with GNU date:

echo "last thursday" |awk '{ 
  cmd = sprintf("date -d \"%s\" +\"%%s %%z\"", $0)
  cmd |getline
  hours = substr($2, 2, 2) + substr($2, 4) / 60
  if ($2 ~ /^-/) hours *= -1
  excel = $1/86400 + hours/24 + 25569
  printf "%.9f\n", excel
}'

This is basically the same code, but the date -d no longer has an @ to represent unix epoch (given how capable the string parser is, I'm actually surprised the @ is mandatory; what other date format has 9-10 digits?) and it's now asked for two outputs: the epoch and the time zone offset. You could therefore use e.g. @1234567890 as an input.

Bug

Lotus 1-2-3 (the original spreadsheet software) intentionally treated 1900 as a leap year despite the fact that it was not (this reduced the codebase at a time when every byte counted). Microsoft Excel retained this bug for compatibility, skipping day 60 (the fictitious 1900/02/29), retaining Lotus 1-2-3's mapping of day 59 to 1900/02/28. LibreOffice instead assigned day 60 to 1900/02/28 and pushed all previous days back one.

Any date before 1900/03/01 could be as much as a day off:

Day        Excel   LibreOffice
-1            -1    1899/12/29
 0    1900/01/00*   1899/12/30
 1    1900/01/01    1899/12/31
 2    1900/01/02    1900/01/01
 …
59    1900/02/28    1900/02/27
60    1900/02/29(!) 1900/02/28
61    1900/03/01    1900/03/01

Excel doesn't acknowledge negative dates and has a special definition of the Zeroth of January (1899/12/31) for day zero. Internally, Excel does indeed handle negative dates (they're just numbers after all), but it displays them as numbers since it doesn't know how to display them as dates (nor can it convert older dates into negative numbers). Feb 29 1900, a day that never happened, is recognized by Excel but not LibreOffice.