Ronflonflon datumgenerator

In his legendary 1980s program Ronflonflon, on Dutch public radio, host Jacques Plafond (stage name of Wim T. Schippers) used to not only mention the conventional date of the broadcast, but also that same date converted to months and years in the past. For example in episode 131, which was broadcast on "October 913, 1984; April 718, 1985; February 403, 1986; or April 8th, 1987". It must have been a nasty job to calculate each week! Thanks to modern technology, you now can calculate such idiosyncratic dates with the Ronflonflon Datumcalculator!