Yesterday I took the super-convenient Thameslink from Blackfriars back up to Cambridge for a winter battery-charging ride on my motorcycle. In London the sun was shining but on crossing the border into Hertfordshire we were suddenly plunged into a frosty, foggy winter.

Cambridge was not as bad but once on the road the fog threatened and I tried to flee it, first toward Grantchester then out toward Linton. The frost warning on the dashboard told me to go home and have a cup of hot chocolate by the fire and the temperature was only 1 degree. It must be the coldest I have ever ridden in.

For a week or so the clock on the bike and the GPS have been one hour ahead. Then the tracks of last week’s rides seemed to have been lost. On getting home in the evening I could see that the day’s ride had been saved but dated April 2000. Trying to change Garmin’s time (it thinks we are in daylight saving – hence the wrong time) and the date (you can’t do it) led me to investigate and find the GPS week rollover bug. Its to do with the satellites and the epoch we are in. Posts from Garmin seem to basically say – we’re not going to do anything about it so buy a new unit.