Actually, you have been a Silver member since the beginning of March, when your EB membership year reset. But the cards always have a two-month 'grace period' added on at the end, in case you had a lot of points in the last few days of February that didn't get processed until after your new year started. If you re-qualify Gold at the last minute, they don't want you to lose Gold privileges while they're processing your renewal.

cheers,

Henry