This coming weekend, in the night from Saturday to Sunday at 0300, the clocks go forward by one hour to summer time. Most people are happy the change takes place on Saturday night, so that they can get back into a normal rhythm in time for work on Monday morning.
But what people may not realise is that in fact, it takes three days on average for the body to come into line with the new schedule, according to research carried out for multimedia company Telenet.
Telenet has a monopoly in TV distribution in Flanders, so the results are based on Flemish customers (and some in Brussels). However if the results are correct, they may also be assumed to apply more broadly.
In a normal week, for the purposes of the research meaning a week during winter-time when no changes take place, people switch off the TV to go to bed at 2226 from Monday to Thursday, later at 2311 on Friday, and again slightly earlier on Saturday (2307) and Sunday (2304).
On the weekend of the change to summer time, however, the TV is switched off on Friday as normal, but 26 minutes earlier than usual on Saturday at 2241 – presumably in anticipation of losing an hour’s sleep in the night. On Sunday, switching off time is advanced by 38 minutes to 2229.
And the effect continues through the following week: TV goes off 27 minutes earlier than usual on Monday and Tuesday, before going back to normal by Wednesday. The effect, as measured by TV times, is therefore felt from Friday through to Wednesday.
But those are regional average figures; province by province the differences are huge. Limburg suffers most, turning off the TV up to 78 minutes earlier all the way up to Wednesday or Thursday more than a week after the change. Compare that to 19 minutes in East Flanders, 15 minutes in West Flanders, 12 minutes in Antwerp and only 8 minutes in Flemish Brabant, which includes the figures for Brussels. The report also shows a milder but longer-lasting effect on switching from summer to winter time.
Telenet quotes Dr. Liese Exelmans, who carries out research at the University of Michigan into media use and its effect on sleep patterns:
“In general people believe that an hour more or less sleep doesn’t matter much to them. People have a great deal of difficulty going to bed on time. They feel tired during the day, but have accepted that as normal. From that point of view the results are worth noting: the switch to summer time does seem to have an influence on TV watching. People are well aware of the switch, and make adjustments to their daily rituals. These results show that the switch to winter and summer time are powerful stimuli that can influence well-established habits.”