The following buffs are applied to all bases in Wars:

 
Duration - May 14 - May 28
+20% Tower Attack
+20% Tower HP
+20% Fire Elemental Resist
+20% Dark Elemental Resist
 
Duration - May 28 - June 11
+20% Tower Attack
+20% Tower HP
+20% Earth Elemental Resist
+20% Wind Elemental Resist
 
Duration - June 11 - July 25
+20% Tower Attack
+20% Tower HP
+20% Ice Elemental Resist
+20% Fire Elemental Resist
 
Duration - July 25 - July 9
+20% Tower Attack
+20% Tower HP
+20% Wind Elemental Resist
+20% Dark Elemental Resist
 
Duration - July 25 - July 9
+20% Tower Attack
+20% Tower HP
+20% Earth Elemental Resist
+20% Ice Elemental Resist