christmas前面的介词什么时候用on 什么时候用at

表示“在圣诞节”有两种说法：at Christmas, on Christmas Day(注意两者在搭配上的差异).如：
We had a good time at Christmas. 我们圣诞节过得很愉快.
We had a party on Christmas Day. 圣诞节我们开了个晚会.
【注】Christmas Eve 指“圣诞节前夕”或“圣诞夜”,其前也用介词 on.如：
I had a good time on Christmas Eve. 圣诞夜我过得很愉快.
at christmas是指“在圣诞节期间”,指节日“当天”才用介词on,如on New Year's day（元旦那
天）,on Christmas Day (on Christmas-day（圣诞节那天）,on Christmas Eve(on Christmas
圣诞节前夕）.