The value on Unix is the number of seconds that have passed since January 1, 1970, 00:00.
Excel uses a similar calculation for date values. However, Excel calculates its date value based on January 1, 1900, and Excel encodes its timestamps as fractions of days instead of seconds. The days and hours appear before the decimal point, and minutes and seconds can be found in the fractions.
So to make a meaningful date out of this number, simply divide the value by the number of seconds a day has (24*60*60 or 86400) and add the days from January 1, 1900, to January 1, 1970 (25569 days).
Assuming the Unix timestamp is in the A1 field, use the following formula to convert the UNIX timestamp from A1 to an Excel date. = A1 / 86400 + 25569
At first, the result will appear as another number. But once you change the cell format cells with a right-click and Format Cells - Date to Time format, the date will be shown in the desired format.