The average employee in Wales works an extra 6.2 hours per week - adding up to an extra £735m-worth of value to the Welsh economy.
"That's a huge amount of hours," said Rhianydd Wiliams from Wales TUC.
"We're asking employers to recognise these extra hours and maybe looking at better ways of managing time within the office so that people feel they can leave on time or have a proper lunch break."
More top news
The historic Llangollen chain bridge, which is thought to be the 'oldest in the world' will re-open today after 30 years of disuse.
Wales have confirmed that 19-year-old uncapped Newport Gwent Dragons centre Tyler Morgan will be part of their World Cup training squad.
A largely dry expected with just a risk of showers along the North Wales coast. Winds will remain fairly strong.