I have two timestamps which describe the same instant of time in two different formats.
2010-10-03 18:58:07 and 2010-10-03T16:58:07.000+02:00
I had the same issue as you and the best way I found is to parse the data. I originally had this format: 2018-01-22 09:25:14.000 +0000
Simply select the column and click on "Text to Columns" in Data's tab.
I used Delimited with space to parse this format in 3 different columns. So at the end, I have;
Col A 2018-01-22 Col B 09:25:14.000 Col C +0000