Fast Overlaps example using the data.table package's foverlaps() function. Uses lubridate to convert text values for date and time to POSIXct

foverlaps example.r

require(data.table)
require(lubridate)

#create the data frames

#x is a data table with a list of events to match against the different dates in x to see if there is overlap
x = data.table(
  eventid=c(1,2,3),
  start  =mdy_hms(c('10/1/2016 04:30:00','10/1/2016 18:02:00','10/2/2016 14:21:00')),
  end    =mdy_hms(c('10/1/2016 05:43:00','10/2/2016 01:23:00','10/4/2016 08:54:00'))
)

#y is a data table with a list of all dates
y = data.table(
  date =c('10/1/2016','10/2/2016','10/3/2016','10/4/2016','10/5/2016','10/6/2016'),
  start=mdy_hms(c('10/1/2016 00:00:00','10/2/2016 00:00:00','10/3/2016 00:00:00','10/4/2016 00:00:00','10/5/2016 00:00:00','10/6/2016 00:00:00')),
  end  =mdy_hms(c('10/1/2016 23:59:59','10/2/2016 23:59:59','10/3/2016 23:59:59','10/4/2016 23:59:59','10/5/2016 23:59:59','10/6/2016 23:59:59'))
  )

#set the key on y to match with
setkey(y,start,end)

#use the foverlaps function to match
#
#note that eventid 1 matches one date only
#          eventid 2 matches two dates
#          eventid 3 matches three dates
#
result <- foverlaps(x,y,type="any")

#show results
x
y
result