"use predefined A51 macros, such as __date__ and __time__"

Yes - and 'C' has similar definitions.
I use these in a file called timestamp.c, and set the 'Always Build' options for that file in the uVision Project.

Was your question just about this time-stamping, or did you want more change control?

In a previous thread, I mentioned QVCS - this is simple, lightweight, and cheap (possibly even free - check the licence terms for your intended usage)

Another useful tool for free, DIY, version control is the MS-DOS Archive Attribute - this is set automatically by the file system whenever a file is modified.
This MS-DOS command line will list all modified files in a directory structure:

DIR /aa /s /b

The /b gives you the listing in "bare" format - without the usual header & trailer info, one file per line with its relative path.

Use the attrib command to "manually" alter file attributes.

The /a and /m options make xcopy selectively copy only modified files:
/a copies only modified files;
/m copies only modified files, and clears the Archive Attribute on the source files when its done.
The /e switch makes xcopy include empty folders - so you can recreate your full folder structure while only copying modified files

PKZIP and WinZip both have options for selecting files by Attribute.