Ajanlaskua

Ajanlaskua, literally "time calculation" in Finnish, is the field or practice of measuring, dating and organizing time. In Finnish usage, ajanlasku refers to calendars, era counting, and the chronological systems used to place events on a timeline. The term combines ajan ("time") and lasku ("calculation" or "deduction").

It covers calendars, era conventions, epoch points from which years are counted, and methods for dating historical events, astronomical observations, and genealogical records. In practice, ajanlaskua includes notation like BCE/CE or the Finnish abbreviations eKr. and jKr., indicating before and after the chosen epoch. It also encompasses broader concepts of chronology, epoch-making events, and the organization of time across cultures.

Historically, timekeeping systems emerged from astronomy and civil administration. The major Western reform is the switch from the Julian to the Gregorian calendar in many regions; Finland, then part of Sweden, adopted Gregorian in 1753, moving from the older calendar sequence and skipping days during the transition. This reform influenced how dates are recorded and interpreted in Finnish sources.

Today, ajanlaskua is used in education, history, archaeology, and museums to date artifacts, events and biographies. It underpins chronologies in Finnish literature and science and is often discussed in cross-cultural contexts where different calendar traditions interact. The concept remains central to scholarly work, archival practice, and public understanding of historical timelines.