Season 14 EU:

What
When
Season 14 [EU] Signups Open
5th of November (20:00 CET)
Season 14 [EU] Signups Close
13th of December (23:59 CET)
Season 14 [EU] Seeding
14th of December
Season 14 [EU] Round 1 starts
4th of January
Season 14 [EU] Round 10 starts (last round)
8th of March
Last date to play regular season games
19th of March
Season 14 [EU] Draw Show
21st of March
Season 14 [EU] Playoff Group Stage starts
22nd of March
Season 14 [EU] Rare Cup Finals
10th of April
Season 14 [EU] Epic Cup Finals
11th of April
Season 14 [EU] Legendary Cup Finals
17th of April
Season 14 [EU] Mythic Championship Finals
18th of April
Season 14 [EU] Playoffs end
18th of April

Season 6 NA:

What
When
Season 6 [NA] Signups Open
6th of September
Season 6 [NA] Signups Close
25th of October
Season 6 [NA] Seeding
26th of October
Season 6 [NA] Round 1 starts
9th of November
Season 6 [NA] Round 8 starts (last round)
18th of January
Last date to play regular season games
29th of January
Season 6 [NA] Draw Show
31st of January
Season 6 [NA] Playoff Group Stage starts
1st of February
Season 6 [NA] Epic Cup Group Stage
1st of February - 19th of February
Season 6 [NA] Epic Cup Finals
21st of February
Season 6 [NA] Legendary and Mythic Group Stage
1st of February - 25th of February
Season 6 [NA] Legendary Cup Finals
27th of February
Season 6 [NA] Mythic Championship Finals
28th of February
Season 6 [NA] Playoff Ends
28th of February

Season 13 EU:

What
When
Season 13 [EU] Signups Open
5th of July (20:00 CEST)
Season 13 [EU] Signups Close
9th of August (23:59 CEST)
Season 13 [EU] Seeding
10th of August
Season 13 [EU] Round 1 starts
24th of August
Season 13 [EU] Round 10 starts (last round)
26th of October
Last date to play regular season games
6th of November
Season 13 [EU] Draw Show
8th of November
Season 13 [EU] Playoff Group Stage starts
9th of November
Season 13 [EU] Rare Cup Finals
28th of November
Season 13 [EU] Epic Cup Finals
29th of November
Season 13 [EU] Legendary Cup Finals
5th of December
Season 13 [EU] Mythic Championship Finals
6th of December
Season 13 [EU] Playoffs end
6th of December

Season 5 NA:

What
When
Season 5 [NA] Signups Open
19th of April
Season 5 [NA] Signups Close
21st of June
Season 5 [NA] Seeding
22nd of June
Season 5 [NA] Round 1 starts
6th of July
Season 5 [NA] Round 8 starts (last round)
24th of August
Last day to submit replays
4th of September
Season 5 [NA] Draw Show
6th of September
Season 5 [NA] Playoff Group Stage starts
7th of September
Season 5 [NA] Epic Cup Group Stage
7th of September - 1st of October
Season 5 [NA] Epic Cup Finals
4th of October
Season 5 [NA] Legendary and Mythic Group Stage
7th of September - 8th of October
Season 5 [NA] Legendary Cup Finals
10th of October
Season 5 [NA] Mythic Championship Finals
11th of October
Season 5 [NA] Playoff Ends
11th of October