Manava Dharmashastra 1.83

1.83

adharmasya rogakāraṇāsyābhāvādarogāḥ | 'rogo' vyādhiḥ | sarva eva catvāro varṇāḥ siddhābhipretārthāḥ | arthaḥ prayojanam | athavā sarve'rthāḥ siddhāḥ yeṣāṃ kāmyānāṃ karmaṇām | pratibandhakābhāvādavyākṣepeṇāśeṣaphalasiddhiḥ | caturvarṣaśatāyuṣa iti | "nanu 'sa ha ṣoḍaśaṃ varṣaśatamajīvaditi' paramamāyurvede śrūyate |" ata evāhuḥ | varṣaśataśabdo'tra vayo'vasthāpratipādakaḥ | catvāri vayāṃsi jīvantīti, na purāyuṣaḥ pramīyante, nāprāpya caturthaṃ vayo mriyante | ataeva dvitīye ślokārdhe vayo hrasatītyāha | pūrvatra vayaso vṛddhāvuktāyāmuttaratra tasyaiva hrāsābhidhānopapattiḥ | pādaśa iti | na cātra caturtho bhāgaḥ pādaḥ, kiṃ tarhi, bhāgamātramaṃśata āyuḥ kṣīyata ityarthaḥ | tathā ca kecidbhālā mriyante kecittaruṇāḥ kecitprāptajarasaḥ | paripūrṇamāyurdurlabham |

as regards the term ‘Samvatsara’, ‘year’, we find that, on the basis of diverse calculations, known as the ‘Saura’, the ‘Sāvana’ and so forth, it is often used in a sense other than that of a collection of exactly three hundred and sixty day; so that it is only right that this term (and not the term ‘fifty-five’) should be taken figuratively, as being descriptive of ‘days’.