This event begins 06/01/2019 and repeats every year forever
Tom Jennings, creator of FidoNet, officially releases the FidoNet software this month in 1984. Soon after its release, dozens of BBSs would use it to link message bases and email via late night modem to modem communication.
FidoNet would eventually grow into a worldwide network of BBSs that's still in use today. At its peak, in 1996, FidoNet had approximately 39,000 participating systems worldwide. More information on FidoNet is available here.