That date is called, in a rather community-spirited manner, the National TV Retune. It's where customers who receive digital channels through their aerial - Freeview - suddenly stop receiving a whole load of them and have to enter their Freeview receiver's setup menu to perform the retune.
The reason for the National TV Retune is that Freeview - that is, the UK's digital terrestrial (ground- based) television service - is an evolving system and a great deal of technical shifting around of TV and radio channels is required to:
- Allow Channel 5 ('Five') to be received everywhere on Freeview. This is a legal requirement as 'Five' is a public service broadcaster (PSB) like the BBC, ITV and Channel 4. As a PSB, Five is granted the right to be received everywhere digitally by Act of Parliament. It's important - whole swathes of the nation have missed out on its launch by the Spice Girls in 1997 and its evolution from original 'stripped and stranded' schedule to the very competent fairly upmarket format broadcast today.
- Empty one of the signal multiplexes completely so it can be re-calibrated to the new DVB-S2 format to support future HD channels (huzzah!). The existing channels on that multiplex (called 'Multiplex B') will be moved to some of the other 5 multiplexes which will themselves be re-calibrated to support them - and in the process make redundant a lot of old Freeview equipment.
- Take the channel information data (called the 'Network Information Table' or 'NIT' - the source of data that provides the channel line-up) , and split it into two because one can't support many more channels - and in the process make redundant a load more old Freeview equipment.
Let's just say that these signals need to be picked up more cleanly (and more strongly) so some customers with doddery old TV aerials that nevertheless picked up Freeview will probably find the service less reliable.
Some old Freeview equipment won't understand the re-calibrated signals so won't be able to receive them anyway. Add to that the splitting of the channel information data ('NIT') and it means that, on these boxes, whole swathes of channels will simply disappear. Now that will generate phone calls!
Some customers who pick up Freeview channels today on a relay station will actually lose some channels. So its goodbye to Poirot and other ITV gems unless you point your aerial to a main transmitter rather than a relay (if you can) to continue picking up ITV3 and ITV4.
I hope you're getting my message; it's all a bit of a mess which we (Tesco and others) have to mop up. As a technologist of course I understand why it's happening, and I know it is all for the future good.
The trouble is that Freeview is chosen by the least tech-savvy of the nation. After all if you're "into" TV then you'll have Sky or Freesat - and both Sky and Freesat offer automated updates of the channel line-up.
Freeview viewers do get a great channel line-up so it's certainly worth having over analogue - even my 96-year old Gran has it. She lives in Bournemouth and is an "old Tory" who is looking forward to watching the live Conservative Conference next week on channel 81, bless her.
Despite living most of her life with zero, then one, then two TV channels, she loves Freeview as she enjoys her politics and is hooked on the BBC Parliament channel.
Unless my Mum can work out how to retune her TV (with me on the phone if necessary) then Gran hasn't a hope of watching.
Tesco is standing by to help our other customers.