60 Seconds Shown in Timestamp

[utkonos]

In one file, the timestamp returned for "Zip Modify Date" is 2020:05:06 01:22:60

This appears to be a bug. If it's not a bug, should the seconds component of the timestamp be considered the same as 00?

Here is the output from 12.00, and I have checked using the latest 12.01. Both have the same output. Also, I have tested this on macOS and Windows. Same results.

$ exiftool P.O.xlsx
ExifTool Version Number         : 12.00
File Name                       : P.O.xlsx
Directory                       : .
File Size                       : 11 kB
File Modification Date/Time     : 2020:05:07 07:19:00-04:00
File Access Date/Time           : 2020:07:22 10:32:30-04:00
File Inode Change Date/Time     : 2020:07:20 15:28:02-04:00
File Permissions                : rwxr-xr-x
File Type                       : XLSX
File Type Extension             : xlsx
MIME Type                       : application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
Zip Required Version            : 20
Zip Bit Flag                    : 0x0002
Zip Compression                 : Deflated
Zip Modify Date                 : 2020:05:06 01:22:60
Zip CRC                         : 0xd07cf71a
Zip Compressed Size             : 388
Zip Uncompressed Size           : 1505
Zip File Name                   : [Content_Types].xml
Creator                         :
Last Modified By                :
Create Date                     : 2006:09:16 00:00:00Z
Modify Date                     : 2020:05:05 14:24:23Z
Application                     : Microsoft Excel
Doc Security                    : None
Scale Crop                      : No
Heading Pairs                   : Worksheets, 1
Titles Of Parts                 : Sheet2
Links Up To Date                : No
Shared Doc                      : No
Hyperlinks Changed              : No
App Version                     : 12.0000



$ exiftool -ver
12.00

[Phil Harvey]

That's odd.  The ZIP file date/time conversion is not subject to round-off errors, so this must have been the way it was stored.  I don't think there is anything that should be changed in ExifTool for this.  The seconds are stored separately in 5 bits of the date/time value, with a resolution of 2 seconds.  Maybe the writing software rounded up from 59 to 60 since odd seconds can't be represented?

- Phil