Best way costs money. Here's the simple way. In B2, you specify start date, and in C2 you put the number of days.
Below, you list each activity and the begin/end dates. That drives the conditional formatting to create your chart. The conditional formatting applies to the entire range.
| A | B | C | D | E | F | G | H | I | J | K | L | M | N |
| Start Date | Interval | | | | | | | | | | | | |
| | | | | | | | | | | | | | |
| | | | | | | | | | | | | | |
Activity | From | To | | | | | | | | | | | | |
| | | | | | | | | | | | | | |
Management | | | | | | | | | | | | | | |
Execution | | | | | | | | | | | | | | |
Evaluation | | | | | | | | | | | | | | |
<colgroup><col style="font-weight:bold; width:30px; "><col style="width:89px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"><col style="width:64px;"></colgroup><tbody>
[TD="bgcolor: #cacaca, align: center"]1[/TD]
[TD="bgcolor: #cacaca, align: center"]2[/TD]
[TD="align: right"]31-Jul[/TD]
[TD="align: right"]15[/TD]
[TD="bgcolor: #cacaca, align: center"]3[/TD]
[TD="bgcolor: #cacaca, align: center"]4[/TD]
[TD="align: right"]31-Jul[/TD]
[TD="align: right"]15-Aug[/TD]
[TD="align: right"]30-Aug[/TD]
[TD="align: right"]14-Sep[/TD]
[TD="align: right"]29-Sep[/TD]
[TD="align: right"]14-Oct[/TD]
[TD="align: right"]29-Oct[/TD]
[TD="align: right"]13-Nov[/TD]
[TD="align: right"]28-Nov[/TD]
[TD="align: right"]13-Dec[/TD]
[TD="align: right"]28-Dec[/TD]
[TD="bgcolor: #cacaca, align: center"]5[/TD]
[TD="bgcolor: #cacaca, align: center"]6[/TD]
[TD="align: right"]15-Aug[/TD]
[TD="align: right"]30-Oct[/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #cacaca, align: center"]7[/TD]
[TD="align: right"]19-Aug[/TD]
[TD="align: right"]20-Nov[/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #cacaca, align: center"]8[/TD]
[TD="align: right"]2-Nov[/TD]
[TD="align: right"]15-Dec[/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
[TD="bgcolor: #0070c0"] [/TD]
</tbody>