What if Lent weren't focused on negatives – giving things up – but on positively affecting the world for good?

The straightforward answer is that it's always been a time for paring away inessentials – luxuries included – and focusing on Christ.

According to Christian charity Stewardship, however, that's not all it can be. Now in its eighth year, its 40acts campaign encourages people to perform an act of kindness every day during Lent.

Supporters can sign up to the challenge online and there are now more than 110,000 subscribers who between them have been the catalyst for more than 4 million acts of generosity across 180 countries.

Everyone who signs up gets a daily email written by a Christian leader, among them this year – for the first time – the Archbishops of Canterbury and York.

40acts co-ordinator Debbie Wright said: 'Every year we have been blown away by the number of people grasping the vision for 40acts and taking the opportunity to show simple acts of generosity in their communities, families and workplaces. We are delighted that this year both archbishops will be joining a number of other fantastic contributors to encourage even greater numbers of people to join the movement.'

Acts of kindness are graded using a traffic light system, with green for acts taking five minutes or less, yellow for acts a little more challenging and costing a few pounds, and red for for 'those who love to push themselves to extravagance' or who have done 40acts before.

Acts can be shared on social media. Stewardship has released resources for church groups, small groups and families. So far more than 3,500 schools have registered to take part.

Individual participants can sign up to 40acts via 40acts.org.uk.