Releases of NetHack and its predecessor Hack, with the date and a link to the annoucement, when I found them. Some timestamps might be wrong.

nethack_release.txt

17-Dec-84 19:26:34     Hack 1.0
21-Jan-85 21:44:28     Hack 1.0.1
01-Apr-85 22:31:25     Hack 1.0.2
23-Jul-85 16:24:17 EDT Hack 1.0.3
28-Jul-87              NetHack 1.3d
15-Aug-87              NetHack 1.4f
03-Dec-87              Nethack 2.2a
09-Apr-88 18:45:41 GMT Nethack 2.3e
24-Jul-89              Nethack 3.0.0
03-Aug-89              Nethack 3.0.1 [Announcement][1]
18-Aug-89              NetHack 3.0.2
07-Sep-89              Nethack 3.0.3 [Announcement][2]
29-Sep-89              Nethack 3.0.4
17-Oct-89              NetHack 3.0.5
22-Nov-89              NetHack 3.0.6
24-Feb-90              NetHack 3.0.7
05-Jun-90              NetHack 3.0.8
29-Jun-90              Nethack 3.0.9
06-Feb-91              Nethack 3.0.10
26-Jan-93              NetHack 3.1.0 [Announcement][3]
06-Mar-93              NetHack 3.1.1 [Announcement][4]
11-Jun-93              NetHack 3.1.2 [Announcement][5]
21-Jul-93              NetHack 3.1.3 [Announcement][6]
18-Avr-96              Nethack 3.2.0
16-Jun-96              NetHack 3.2.1
15/18Dec-96            NetHack 3.2.2
10-Dec-99              NetHack 3.2.3
10-Dec-99              NetHack 3.3.0
??-Oct-00              NetHack 3.3.1
22-Mar-02              NetHack 3.4.0
23-Feb-03              NetHack 3.4.1
31-Aug-03              NetHack 3.4.2
08-Dec-03              NetHack 3.4.3

[1]: groups.google.com/group/comp.sources.games/browse_frm/thread/843cceea77fa3183/1fa24657e38640eb?lnk=gst&q=nethack+Patch+1#1fa24657e38640eb
[2]: groups.google.com/group/comp.sources.games/browse_frm/thread/ea8d52c7185d925f/24a74c0476417b31?lnk=gst&q=nethack+3.0+Patch+3#24a74c0476417b31
[3]: groups.google.com/group/comp.sources.games/browse_frm/thread/9abb36b69930656d/5ef7a2f117e0efa9?lnk=gst&q=nethack+3.1#5ef7a2f117e0efa9
[4]: groups.google.com/group/comp.sources.games/browse_frm/thread/dca7511d0ebef103/286fc101db88e3b8?lnk=gst&q=nethack+3.1+Patch+1#286fc101db88e3b8
[5]: groups.google.com/group/comp.sources.games/browse_frm/thread/610dbf8aa21cb780/cac7871f57f9df19?lnk=gst&q=nethack+3.1+Patch+1#cac7871f57f9df19
[6]: groups.google.com/group/comp.sources.games/browse_frm/thread/ea1c5d0b9cc96a6f/9073e4c12c393195?lnk=gst&q=nethack+3.1+Patch+1#9073e4c12c393195