Not able to create index using DATE_ADD_MILLIS function

I am trying to create index using
CREATE INDEX notifications-projectid-days ON notifications(createdTime) where createdTime > DATE_ADD_MILLIS(CLOCK_MILLIS(), -7, ‘day’)
It throws an error saying - “Expression not indexable: (DATE_ADD_MILLIS(CLOCK_MILLIS(“UTC”), (-7), “day”) < createdTime) - at end of input”
I read somewhere that CLOCK_MILLIS cannot be used to created index, is there any other way to get the current system time to create the index?

But the select statement with same where clause works
Please help me with this.

CLOCK_MILLIS() is variant and you can’t use in the index.

Yes I have read about it, any way to get the current system time to create indexes?