日期时间偏移

dt_add(字段名, dt1=None, dt2=None, year(s)=None, month(s)=None, day(s)=None, hour(s)=None, minute(s)=None, second(s)=None, microsecond(s)=None, weeks(s)=None, weekday=None)

year(s)、month(s)、day(s)等参数的后面都带有s，表示这些参数可以有两种形式，即year和years，month和months等。以year和years为例，如果参数传递的是year，表示在年份粒度上覆盖为year参数的值；如果传递的是years，表示在年份粒度上增加years参数的值。同时要一起组合使用的dt_add函数支持在特定时间粒度上修改（增加、减少、覆盖）日期时间的值。

{
    "time1" : "2019-06-04 2:41:26"
}

e_set("time2", dt_add(v("time1"), year=2018))

{
	"time1": "2019-06-04 2:41:26",
	"time2": "2018-06-04 02:41:26"
}

e_set("time2", dt_add(v("time1"), years=2018))

{
	"time1": "2019-06-04 2:41:26",
	"time2": "4037-06-04 02:41:26"
}

{
    "time1" : "2019-06-04 2:41:26"
}

#time1的下一个星期一对应的日期
e_set("nex_Monday", dt_add(v("time1"), weekday=dt_MO(1)))

#time1的上一个星期二对应的日期
e_set("previous_Tuesday", dt_add(v("time1"), weekday=dt_TU(op_neg(1))))

#time1的下下一个星期六对应的日期
e_set("nex_next_Saturday", dt_add(v("time1"), weekday=dt_SA(2)))

#time1的上上一个星期日对应的日期
e_set("previous_previous_Sunday", dt_add(v("time1"), weekday=dt_SU(op_neg(2))))

{
	"time1": "2019-06-04 2:41:26",
	"previous_Tuesday": "2019-05-28 02:41:26",
	"previous_previous_Sunday": "2019-05-26 02:41:26",
	"nex_next_Saturday": "2019-06-15 02:41:26",
	"nex_Monday": "2019-06-10 02:41:26"
}