The .tgz file is about 140k; tell Netscape to save it as "source", without any tampering with it, and it should work.
Some of the documentation files contained within it:
Calendar software: C code to do date-of-Easter calculations and liturgical calendars. easter.txt is the documentation or how-to-use file. (This used to be easter.doc, as good UNIX documentation files should be named, but nowadays, that extension gets interpreted by browsers as the format of a certain popular word-processor.)
The tar-file is jd.tar , and in gnu-compressed form, it is jd.tgz .
Planetary positions as of about an hour ago:
Some practical astronomy: