Maienzug (Aarau, Switzerland) takes place every year on the first Friday in July. It's an example of a moveable feast, that is, a holiday that is not on the same date every year. The following is a list of holidays with fixed dates which are celebrated by heathens or heathen-derived cultures.

June
8
Lindisfarne Day (American Asatru, American Odinist)

9
Day of Sigurd (American Asatru, American Odinist)

21
Midsummer (Urglaawe, England),
Hleifblot (American Asatru),
Líða (Theod),
Mittesommer (Germany),
Sommersonnewende (Germany),
Hochsommer Fest (Switzerland),
Midsommar (Norway),
Midsommardagen (Sweden)   

July
7
Lindenfest begins (Geisenheim, Germany)

9
Day of Unn the Deep-Minded (American Asatru), Lindenfest ends (Geisenheim, Germany)

15 Month of possible date of Hoietfescht begins (Urglaawe)

29 Stikkelstad Day (American Asatru)

31 Month of possible date of Honoring of the Weisskeppichi Fraa ends (Urglaawe)

Some moveable feasts require knowing the date of other feasts to derive their dates. Pinkster is on the fiftieth day after Easter, aka Whitsunday (in Deventer, province of Overijssel, Netherlands)
Pinkster Bruid or Pinksterbloem on Whit Tuesday (in Volte, Ootmarsum, Markelo, Rijssen, Hellendoorn, Hengelo, and other communities, province of Overijssel, Netherlands.)

Some of my readers may be wondering why I include American Odinist celebrations.  In creating these calendars, I've endeavored to make them broadly useful to heathens and others across many traditions, so, I'm trying to describe holidays that are currently celebrated by heathen groups or by heathen derived cultures, whether I'm interested in celebrating them myself or not. I'm not trying to prescribe which holidays to celebrate. (Note: USA Odinism and UK Odinism are different from each other.)

Image: Sif harvest basket, containing wheat harvested in June, photo by Erin Lale