On my iPhone I make pictures using Darkroom Premium. Since I use this software and not the standard application the EXIF data is not stored in the pictures. Not having the GPS information is not such a big problem. But not having a date and time is!

In this specific situation the file date and time corresponds with the date and time at which the picture was taken. To correct this on my PC I use a script that copies the file date to some EXIF fields.
The script uses exiftool by Phil Harvey which is a brilliant piece of software when you want to manipulate the metadata of a picture

(1) "C:\Program Files\exiftool\exiftool.exe" "-FileModifyDate>CreateDate" *.jpg
(2) "C:\Program Files\exiftool\exiftool.exe" "-CreateDate>DateTimeOriginal" *.jpg
(3) "C:\Program Files\exiftool\exiftool.exe" "-CreateDate>ModifyDate" *.jpg
(4) "C:\Program Files\exiftool\exiftool.exe" "-CreateDate>FileModifyDate" *.jpg

Remarks:

C:\Program Files\exiftool\ is the location of exiftool.
*.jpg are the files that need to be updated.

First the file modify date (FileModifyDate) is copied to the EXIF field CreateDate (1).

Then the  CreateDate is copied to DateTimeOriginal and ModifyDate (2 and 3).

By this changes the change date of the file is modified. Because of this this field (FileModifyDate) is restored again (4).

After the first copy action the field CreateDate is being used. This will not change during the script. The file date (FileModifyDate) will change with every operation. If you use this as “source” the EXIF fields will contain three different dates. You probably do not want this to happen