How to make a time series in R by counting entries from a given vector? [duplicate]

I have a vector like this:

created_time
2016-01-18T08:05:44+0000
2016-01-18T08:05:44+0000
2016-01-18T08:05:44+0000
2016-02-23T01:42:48+0000
2016-02-23T03:51:37+0000
2016-02-23T09:49:01+0000
2016-02-23T10:09:32+0000
2016-02-26T07:45:10+0000
2016-02-26T11:48:09+0000
2016-02-27T03:27:39+0000
2016-02-28T09:28:16+0000
2016-03-02T00:17:14+0000
2016-03-02T05:34:41+0000
2016-03-02T09:04:45+0000
2016-03-02T11:18:28+0000

And I want to build a time series with the day (or month or year) followed by the number of occurrences in that day (or month or year). For this data I would want to have a time series like this:

created_time, occurr
2016-01-18, 3
2016-02-23, 4
2016-02-26, 2
2016-02-27, 1
2016-02-28, 1
2016-03-02, 4

Than I would need to plot a histogram with this. Can anyone help me please? Thanks