Update release dates.

wiki/src/contribute/calendar.mdwn

@@ -12,7 +12,7 @@ All times are referenced to Berlin and Paris time.
 
 * 2018-05-04, 14:00: Additional Software team meeting
 
-* 2018-05-08: **Release 3.7** (Firefox 52.8, bugfix release) — bertagaz is the RM
+* 2018-05-09: **Release 3.7** (Firefox 52.8, bugfix release) — bertagaz is the RM
 
 * 2018-06-01: Beta release of VeraCrypt
 
@@ -20,9 +20,9 @@ All times are referenced to Berlin and Paris time.
 
 * 2018-06-06, 19:00: [[Contributors meeting|contribute/meetings]]
 
-## 2018Q3
+* 2018-06-26: **Release 3.8** (Firefox 52.9, bugfix release) — intrigeri is the RM
 
-* 2018-07-03: **Release 3.8** (Firefox 52.9, bugfix release) — intrigeri is the RM
+## 2018Q3
 
 * 2018-07-03, 19:00: [[Contributors meeting|contribute/meetings]]
 
@@ -39,11 +39,11 @@ All times are referenced to Berlin and Paris time.
 
 * 2018-08-17: Release 3.9~rc1 — anonym
 
-* 2018-08-28: **Release 3.9** (Firefox 60.2, major release) — anonym is the RM
+* 2018-08-21: **Release 3.9** (Firefox 60.2, major release) — anonym is the RM
   - includes VeraCrypt support + major Additional Software Packages improvements
 
 ## 2018Q4
 
-* 2018-10-23: **Release 3.10** (Firefox 60.3, bugfix release) — anonym is the RM
+* 2018-10-16: **Release 3.10** (Firefox 60.3, bugfix release) — anonym is the RM
 
 * 2018-11-27: **Release 3.11** (Firefox 60.4, major release) — anonym is the RM