,----------------+-------+--------+----------.
| Task           | Start | End    | Duration |
+----------------+-------+--------+----------+
| Contribution 1 | Jan 1 | Jan 30 | 30 days  |
+----------------+-------+--------+----------+
| Contribution 2 | Mar 1 | Mar 10 | 10 days  |
+----------------+-------+--------+----------+
| Contribution 3 | Apr 1 | May 30 | 60 days  |
`----------------+-------+--------+----------'