相对于我们熟悉的首日封,次日封就是我们比较陌生的东西了。所谓次日封,就是某套邮票首发日第二天贴该票寄发的信封。它产生的原因大概有三种。其一,新邮不能在首日到货或售出,集邮者只能在首发次日购到新邮。如西安邮友寄我的《陶行知诞生一百周年》邮票次日封(图1),寄封者明确在封背记录(图2),邮票在当地为次日到货出售。其二,接收邮局 Relative to our familiar first day cover, the next day cover is something we are more strange. The so-called next-day cover, is the first day of a set of stamps posted the envelope sent the next day. It produces about three reasons. First, the new mail can not arrive or be sold on the first day, and the stamp collector can only purchase the new mail on the next day. For example, Xi’an Post sent me a postage stamp on the “100th Anniversary of the Birth of Tao Xingzhi” (Figure 1). The sender of the stamp was clearly marked on the back (Figure 2). The stamps were for sale at the local place for the next day. Second, receive the post office