Usum

Usum téh salah sahiji babagian utama taun, biasana mah dumasar bentuk iklim nu lega. Ilaharna sataun kabagi jadi opat usum, nyaéta: usum semi, usum panas, usum gugur, jeung usum tiris. Ngan, di Indonésia mah lantaran nganjrek di daérah tropis, mangka ngan dibagi jadi dua usum wungkul, nyaéta: usum ngijih jeung usum halodo.

Ari baheula di Mesir Kuna mah usum téh kabagi jadi tilu usum, nyaéta: musim caah, usum darurat lantaran caah, jeung usum panunéian nu panas.

Usum dunya

Tutumbu luar 
 (Basa Inggris) The seasons begin at the time of the solstice or equinox
 (Basa Inggris) Solstice does not signal season's start?
 Australian Weather and Seasons 
 When do the Seasons Begin? (from the Bad Astronomer)
 Solstice does not signal season's start (from The Straight Dope)
 Why the Earth has seasons article on h2g2.
 Aboriginal seasons of Kakadu
 Indigenous seasons (Australian Bureau of Meteorology)
 Mt Stirling Seasons 
 Musim info 
 The Lost Seasons
 Melbourne's six seasons 
 The Lengths of the Seasons (numerical integration analysis)
 Earth distance vs tilt
 Tutorial on Earth/Sun Relations and Seasons 
Cuaca
Kalénder
Hijian wanci