To create a holiday data frame for time series forecast with Prophet, there are many ways, but one way is just writing an R script and run it as a custom R data frame.
Example R script:
tibble::tibble(holiday='special_sale_day',
ds=as.Date(c('2021-01-01', '2021-01-30', '2021-03-30','2021-04-30', '2021-05-30','2021-09-30')),
lower_window = 0,
upper_window = 1)
Then you can specify this holiday data frame from a Prophet forecast step.
