It's important to know that a 'week' in tachograph terms does not have to be aligned with the standard 7 week as we know it (from Sunday till Monday) although it lasts for 7 days. A tachograph week starts at the end of a weekly rest period. So a tachograph week can start on any day of the week.

When should I start a new tachograph?

4) Tachograph Rules – Minimum Rest Each Week

This must begin no later than the end of 6 consecutive 24-hour days from the end of that driver's last weekly rest.

What is the weekly rest period for HGV drivers?

Drivers' hours weekly rest of 45 hours, which can be reduced to 24 hours, provided at least one full rest is taken in any fortnight. There should be no more than six consecutive 24 hour periods between weekly rests.