Simple rule (traditional Jain maryada):

• “First kāl” (pehlo kāl) means the first prahar of the day—about the first 3 hours after your local sunrise.
• For first-kāl use, boil the water only after sunrise and preferably as early as possible, well within this first prahar.
• Do not boil at night. If the water was not boiled in the first prahar, it is not counted as “first-kāl” water in many maryadās.
• Shwetambar: Commonly insist on same‑day, daylight‑boiled water; for first‑kāl, it should be boiled in that first prahar.
• Digambar: Emphasis on freshly prepared, daylight water; usually not kept overnight. Follow your own Āchārya/Saṅgh’s maryadā if they specify a different window.

For simple, practical guidance on “ukalela/boiled water” time, see: and “pehlo kād/prahar” notes here: