DearZhang,
IamreallysorrytotellyouthatIwasunabletoattendyourbirthdaypartyyesterdayevening.Thatisowingtothefactthatmyoldfriendsvisitedmyhousewithouttellingmetheexacttime.Ihadtoentertainthosefriendswithmypassionintheentireevening,andIwillcontinuetoentertaintheminthefollowingtwodays.
IreallyregretthatIhaven'tgotocelebrateyourbirthdaypersonallyandhadmissedawonderfulchancetoenjoymyselfwithourkindcolleages.Ihavepreparedaprettygifttoyouyesterdayandwillsendtoyouthisafternoontoshowmybestbirthdaywishes.Besides,Itrustthatyouwillunderstandme.
Bestwishes,
yourssincerely,
Tom