Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 18: The Advent of Rāma, Lakṣmaṇa, Bharata and Śatrughna
Text 1.18.8

ततो यज्ञे समाप्ते तु ऋतूनां षत्समत्ययुः॥

tato yajñe samāpte tu ṛtūnāṁ ṣat samatyayuḥ

tataḥ = the; yajñe = sacrifice; samāpte tu = after had been completed; ṛtūnām = seasons; ṣat = six; samatyayuḥ = passed.

After the sacrifice had been completed, six seasons passed.