period of variability P The duration of one cycle in a (semi) periodical star. time tijd 时间 attosecond attoseconde centisecond centiseconde day dag 天 day (sidereal) decasecond decaseconde decisecond deciseconde exasecond exaseconde femtosecond femtoseconde gigasecond gigaseconde gigayear gigajaar hectosecond hectoseconde hour uur 小时 hour (sidereal) kilosecond kiloseconde megasecond megaseconde microsecond microseconde millisecond milliseconde minute (sidereal) minute minuut 分钟 nanosecond nanoseconde petasecond petaseconde picosecond picoseconde second (sidereal) second seconde 秒 shake terasecond teraseconde year jaar year (sidereal) year (tropical)