Error in filtering by date in R: object of type 'closure' is not subsettable

I want to create a new variable in my data table in R that will be equal to 1, if the date of the event is after a certain time (2019-01-01) and will be equal to 0 otherwise. I am using the following code:

dt$time <- ifelse[dt$date > '2019-01-01',1,0]

But I am getting a mistake:

object of type 'closure' is not subsettable.

To be honest, I don't understand what is wrong.