How to describe relative dates (from/to fields)

When you create a new data source you are asked to specify the date range for the events (from date/to date). Sometimes the dates are absolute values, e.g. 2015-02-03, but quite frequently they are relevant to the current date and time. EventBlender uses underneath the PHP function strtotime to convert textual representations into absolute times, as shown in the examples below:

All absolute dates were calculated assuming the current date and time is 2016-04-30 13:02:35
Relative Date Description Absolute Date
now   2016-03-08 13:02:35
today   2016-03-08 00:00:00
today +24 hours   2016-03-09 00:00:00
monday this week   2016-03-07 00:00:00
sunday this week   2016-03-13 00:00:00
monday previous week   2016-02-29 00:00:00
sunday previous week   2016-03-06 00:00:00
monday next week   2016-03-14 00:00:00
sunday next week   2016-03-20 00:00:00
first day of this month   2016-03-01 13:02:35
last day of this month   2016-03-31 13:02:35
first day of previous month   2016-02-01 13:02:35
last day of previous month   2016-02-29 13:02:35
first day of next month   2016-04-01 13:02:35
last day of next month   2016-04-30 13:02:35
+0 days   2016-03-08 13:02:35
+7 days   2016-03-15 13:02:35
-7 days   2016-03-01 13:02:35
+1 week   2016-03-15 13:02:35
-1 week   2016-03-01 13:02:35
+2 months   2016-05-08 13:02:35
-6 months   2015-09-08 13:02:35
+1 year   2017-03-08 13:02:35
-5 year   2011-03-08 13:02:35
+1 day +1 week +1 month   2016-04-16 13:02:35