Interesting enquiry, off the top of my head, we don’t have any API available to get the applet publish date from the library.
Our test shows, Utilities.FileSystem.GetFileLastWrite(Utilities.CurrentAppletName) return the last date time applet modified/publish. For example, if you modified the applet on “04 Dec 2009 10.10 AM”, GetFileLastWrite() will return the modified date. Once you update the applet, it will return the last update date.
Another workaround is to store the modified/publish date in the applet, you will need to update the date manually when you modified the applet. For example,
publishDate = Utilities.ISOToDate(“20091127T143836”)