This is the eve of the most "Latvian" of all national holidays, Jāņi or Midsummer, which is the shared name-day of Jānis (June 24) and Līga (a female name, June 23). Jāņi are celebrated the night – all night by tradition– from Līga's day to Jānis' day and the time is often called The Līgo Evening (Līgo vakars). This has less to do with Līga, more with the endless number of friendly mocking, drinking and sometimes bawdy songs sung with the refrain "līgo, līgo", which means to rock or swing. If this is getting complicated to non-Latvians, it should :). If you are not confused enough, ask a Latvian friend to play the old Čikāgas piecīši (a satirical singing group) record with the track in English explaining Jāņi, when «Latvians burn blacktop in barrels".
Anyway, Baltic and Nordic readers will find this familiar, as June 23, by accident of calendar, is also Midsummer in Sweden, Norway, Finland, as well as in Lithuania and Estonia. The Danes are always romping around with beer bottles in their hands (so I remember an evening in Copehagen many years ago) so perhaps there is no special midsummer for them (or am I covering up my ignorance/knowledge with special needs on these matters?).
Unlike the Nordics, who preserve their work week by always celebrating Midsummer on a Friday, Latvians always celebrate June 23-24, which is an ordinary weekend next year, but becomes interesting again in 2008, when the festivities will run again from Friday night to back-to-work Tuesday,
In many other places, the idea of Midsummer (India, for instance, where it is summer all year long)must be strange, and this is just a way of explaining to readers in such places why I am wishing all my readers, etc. who understand what Jāņi/Midsummer is, PLEASE HAVE A SAFE AND GREAT ONE.