April 1: Loki Day. Loki's Day is celebrated on April 1st by American Asatru groups and individuals influenced by the old Ostara festival held by the old Ring of Troth, which was a multi day campout that included April 1st when that date fell on a weekend. Loki Day was a day for pranks and jokes in honor of Loki, and toward the end of the RoT women who were awake in the early morning threw their hair-combings into the fire for Loki. When the Ring of Troth broke into two groups, the American Vinland Association kept the Loki celebrations intact, while over the years the Ring of Troth abandoned them due to the influence of new members who were Nokeans (see my post on Nokeans for a definition and discussion.) The Troth recently re-embraced Loki, so the old custom may or may not come back. Also on April 1st: Narrentag (Germany, Austria, Switzerland) and the season of the possible date of Alp Aufzug begins (Switzerland.)

9 Day of Haakon Sigurdson (American Asatru, American Odinist)

14 Flyttedag, Faredag (Norway)

15 Sechseläuten (Zurich, Switzerland)

21 Sigrblot (Asatru)

22 Yggdrasil Day (American Asatru)

30

Valpurgisnacht (American Asatru),
May Eve (American Asatru, England),
Walpurgisnacht / Wonnenacht (Urglaawe), Wonnezeit begins (Urglaawe),
Walpurgisnacht (Germany, Austria, Switzerland),
Valborgsmässoafton (Sweden)
Valborgsnatten (Norway),
Maitag Vorabend (Switzerland),
Valborgsaften (Jutland, Denmark) 

May

1
May Day (American, English),
Valpurgis / Walburg (American Asatru),
Thrimilci (American Asatru),
Wonnezeit ends (Urglaawe),
Sommer Entdeckung (Germany),
Fluitjes Maken (Ootmarsum, Netherlands)  

9 Day of Gudhrodr of Gudhbrandsdal (American Asatru, American Odinist),
World Odin Prayer Day (Odinist)

12 Observance of Frost Giant Attacks begins (Urglaawe)

14 Observance of Frost Giant Attacks ends (Urglaawe)

20 Frigga Blot (American Asatru)

29 Einherjar’s Day (Folkish American Asatru)

31 season of possible date of Alp Aufzug ends (Switzerland)

Image: photo by Erin Lale titled "A Slice for Lollus," image contains the rune knife Lalaknifr and poppyseed bread.