Delphi stores date and time values in the TDateTime type.
The integral part of a TDateTime value is the number of days
that have passed since 12/30/1899.
The fractional part of a TDateTime value is fraction of
a 24 hour day that has elapsed.
据此,
var t1,t2:tdatetime;x:double;
t1:=第一次故障时间
t2:= 2..........
x:=t2-t1 ;
x的整数部分就是天数,小数部分乘以24=小时的时间