Muhūrt (Sanskrit: मुहूर्त) is a Hindu unit of measurement for time in the Hindu calendar.
In the Brāhmaṇas, muhūrta denotes a division of time: one-thirtieth of a day, or a period of forty-eight minutes. The sense "moment" is also common in the Brāhmanạs. In the Rigveda we only find the sense "moment."
Further each muhūrta is further divided into 30 (Indian) minutes or kalā (making 30 Kalā ≈ 48 western min). Each kalā is further divided into 30 (Indian) seconds or Kāṣṭhā, making 30 Kāṣṭhā ≈ 1.6 western minute.
The "Sandhi Vidchhed" for the term is thus: It breaks muhūrt into two parts, "muhu" (moment/immediate) and "ṛta" (order). The author of Ṛg Ved III.33.5 has accordingly created this descriptive term. Ṛta refers to the natural, yearly order of the seasons, so that the term muhūrt refers to the daily reflection of these. Also, cf., Śatpath Brāhmaṇa X.4.2.18, as below.
The term appears as early as the Ṛg Veda, where, according to Monier Williams, it means "a moment", but does not evidence any specification of an exact periodicity there as received in later works, such as the Śatapatha-Brāhmaṇa, "The One Hundred Path Riddle" or the Taittirīya-Brāhmaṇa, "The Partridge's Riddle".
Pt. Vijay Shrikrishna Jakatdar points to two specific Ṛg Veda passages that employ the term, III.33.5, and III.53.8:
रमध्वं मे वचसे सोम्याय रतावरीरुप मुहूर्तमेवैः | पर सिन्धुमछा बर्हती मनीषावस्युरह्वे कुशिकस्य सूनुः ||
"Linger a little at my friendly bidding rest, Holy Ones, a moment in your journey. With hymn sublime soliciting your favour Kuśika's son hath called unto the River." (trans. Ralph T. H. Griffith)
and
रूपं-रूपं मघवा बोभवीति मायाः कर्ण्वानस्तन्वं परि सवाम | तरिर्यद दिवः परि मुहूर्तमागात सवैर्मन्त्रैरन्र्तुपा रतावा ||