When I was growing up I was told it was rude to be on time. Always be ten minutes late I was told, it's the Irish way of doing things.
This morning I was invited to a 'Come and Meet the Mums in Year 3A' coffee morning - the invitation said 0830. Year 3A has children of all nationalities, with different cultural norms, but even so I didn't arrive until ten minutes after the appointed hour.
As I drove up I was joined by a French mum and two English mums - they'd also been trained from birth to be ten minutes late to a party.
Except the party was being hosted by an American mum and from the strained expression on her face when we all barged in ten minutes late I have come to conclusion that in America, one must be on time. Or one will never be invited again.