{"id":"vidhyamitra:day:1931-09-13:en","page_class":"VM-1-day","url":"https://vidhyamitra.com/day/1931-09-13","language":{"target_lang":"en","base_lang":"en","quality_tier":"canonical"},"data":{"date":"1931-09-13","date_display":"September 13, 1931 CE","panchanga":{"method":"Sūrya Siddhānta + Bhāskara-II iterative manda + Kerala-school (Mādhava-Nīlakaṇṭha) evection + variation + annual equation","engine_version":"2.0 (Kerala-school enhanced)","accuracy_note":"Sub-degree on Moon at any Kali-Yuga date (~2-5° residual max)","tradition_chain":"Āryabhaṭa(499) → Brahmagupta(628) → Bhāskara II(1150) → Mādhava(~1400) → Parameśvara(1430) → Nīlakaṇṭha(1501) → this","input":{"year":1931,"month":9,"day":13,"hour":6,"minute":30,"second":0,"calendar":"gregorian"},"julian_day":2426597.770833,"kali_year":5033,"ahargana":1838132.2708,"sun":{"sidereal_longitude":145.8355,"rashi":5,"rashi_name":"Siṃha"},"moon":{"sidereal_longitude":156.6879,"rashi":6,"rashi_name":"Kanyā"},"tithi":{"number":1,"name":"Pratipada","paksha":"Śukla","full_name":"Śukla Pratipada","elongation_degrees":10.8525,"elapsed_within_tithi_degrees":10.8525},"nakshatra":{"number":12,"name":"Uttara Phalgunī","pada":4,"moon_longitude":156.6879,"elapsed_within_degrees":10.0213},"yoga":{"number":23,"name":"Śubha","sum_longitude":302.5234},"karana":{"half_tithi_index":1,"name":"Bava"},"vara":{"number":2,"name":"Ravivāra (Sunday)"}},"sky":{"method":"Sūrya-Siddhāntic Bhāskara-II 4-step iteration with atan2-based śīghra + varying peripheries + lunar latitude","engine_version":"3.0 (Pūrṇa — complete SS implementation)","tradition_sources":"Āryabhaṭīya 499 CE → SS Ch.1-5 Burgess 1860 → Siddhānta-Śiromaṇi Bhāskara II 1150 → Tantrasaṅgraha Nīlakaṇṭha 1501","input":{"year":1931,"month":9,"day":13,"hour":6,"minute":30,"calendar":"gregorian"},"julian_day":2426597.770833,"ahargana":1838132.2708,"kali_year":5033,"ayanamsa_lahiri":22.8989,"grahas":{"sun":{"sidereal_longitude":146.39247799999998,"rashi":{"number":5,"name":"Siṃha"},"nakshatra":{"number":11,"name":"Pūrva Phalgunī","pada":4},"retrograde":false},"moon":{"sidereal_longitude":158.46957799999996,"rashi":{"number":6,"name":"Kanyā"},"nakshatra":{"number":12,"name":"Uttara Phalgunī","pada":4},"retrograde":false,"latitude":0.7975},"mars":{"sidereal_longitude":185.16297800000007,"rashi":{"number":7,"name":"Tulā"},"nakshatra":{"number":14,"name":"Citrā","pada":4},"retrograde":false},"mercury":{"sidereal_longitude":134.17937799999999,"rashi":{"number":5,"name":"Siṃha"},"nakshatra":{"number":11,"name":"Pūrva Phalgunī","pada":1},"retrograde":false},"jupiter":{"sidereal_longitude":110.10017800000003,"rashi":{"number":4,"name":"Karka"},"nakshatra":{"number":9,"name":"Aśleṣā","pada":2},"retrograde":false},"venus":{"sidereal_longitude":148.680178,"rashi":{"number":5,"name":"Siṃha"},"nakshatra":{"number":12,"name":"Uttara Phalgunī","pada":1},"retrograde":false},"saturn":{"sidereal_longitude":264.2462780000001,"rashi":{"number":9,"name":"Dhanu"},"nakshatra":{"number":20,"name":"Pūrva Āṣāḍhā","pada":4},"retrograde":true},"rahu":{"sidereal_longitude":346.9066,"rashi":{"number":12,"name":"Mīna"},"nakshatra":{"number":27,"name":"Revatī","pada":1},"retrograde":false},"ketu":{"sidereal_longitude":166.9066,"rashi":{"number":6,"name":"Kanyā"},"nakshatra":{"number":13,"name":"Hasta","pada":3},"retrograde":false}},"panchang":{"method":"Sūrya Siddhānta + Bhāskara-II iterative manda + Kerala-school (Mādhava-Nīlakaṇṭha) evection + variation + annual equation","engine_version":"2.0 (Kerala-school enhanced)","accuracy_note":"Sub-degree on Moon at any Kali-Yuga date (~2-5° residual max)","tradition_chain":"Āryabhaṭa(499) → Brahmagupta(628) → Bhāskara II(1150) → Mādhava(~1400) → Parameśvara(1430) → Nīlakaṇṭha(1501) → this","input":{"year":1931,"month":9,"day":13,"hour":6,"minute":30,"second":0,"calendar":"gregorian"},"julian_day":2426597.770833,"kali_year":5033,"ahargana":1838132.2708,"sun":{"sidereal_longitude":145.8355,"rashi":5,"rashi_name":"Siṃha"},"moon":{"sidereal_longitude":156.6879,"rashi":6,"rashi_name":"Kanyā"},"tithi":{"number":1,"name":"Pratipada","paksha":"Śukla","full_name":"Śukla Pratipada","elongation_degrees":10.8525,"elapsed_within_tithi_degrees":10.8525},"nakshatra":{"number":12,"name":"Uttara Phalgunī","pada":4,"moon_longitude":156.6879,"elapsed_within_degrees":10.0213},"yoga":{"number":23,"name":"Śubha","sum_longitude":302.5234},"karana":{"half_tithi_index":1,"name":"Bava"},"vara":{"number":2,"name":"Ravivāra (Sunday)"}},"eclipse_current":{"solar":{"type":"solar","occurs":false,"moon_latitude":0.798,"elongation":10.852},"lunar":{"type":"lunar","occurs":false,"moon_latitude":0.798,"opposition_distance":169.148}},"eclipse_window_40days":[]},"calendars":{"vikram_samvat":1988,"vikram_samvatsara":"Tāraṇa","saka_samvat":1853,"saka_samvatsara":"Prajāpati","bengali_samvat":1338,"malayalam_era":1107,"nanakshahi_year":462,"lunar_month":"Bhādrapada","lunar_month_paksha_full":"Bhādrapada Śukla Pakṣa","solar_month":"Siṃha (Āvaṇi)","ritu":"Varṣā (Monsoon)","display_summary":"Bhādrapada Śukla Pratipada · Vikram 1988 Tāraṇa · Śaka 1853 Prajāpati"},"festivals":[{"id":"simha-sankranti","name":"Siṁha Saṅkrānti","name_sanskrit":"सिंह सङ्क्रान्ति","tradition":"Pan-Hindu","significance":"Sun enters Leo.","vrata":false,"detection":{"sun_rashi":"Siṃha"},"precedence":5}],"todays_walk":{"walk":{"id":"surya-walk","name":"Sūrya Walk","name_sanskrit":"सूर्य यात्रा","type":"graha","description":"Self-illumination + BG 4.1 (Sun-lineage of Gītā transmission).","step_count":6,"url":"/walk/surya-walk"},"reason":"Ravivāra (Sunday) — its presiding graha's walk."},"cosmic_resonances":[]},"validity":{"eternal":false,"valid_from":"1931-09-13T00:00:00Z"},"liturgical":{"opening":"जय श्री कृष्ण","closing":"ॐ तत् सत्","attribution":"Computed by Vidhyamitra Sūrya-Siddhānta substrate; Vidhyamitra substrate"},"seo":{"title":"Pañchāṅga September 13, 1931 CE · Vidhyamitra","description":"Vedic pañchāṅga for September 13, 1931 CE: Śukla Pratipada · Uttara Phalgunī.","schema_org_type":"Article","canonical":"https://vidhyamitra.com/day/1931-09-13","hreflang_alternates":{"en":"https://vidhyamitra.com/day/1931-09-13","sa":"https://sa.vidhyamitra.com/day/1931-09-13","hi":"https://hi.vidhyamitra.com/day/1931-09-13","x-default":"https://vidhyamitra.com/day/1931-09-13"}},"provenance":[{"pillar":"BOB-History","pillar_version":"2.12.0","method":"Sūrya-Siddhānta first-principles + Bhāskara II + Kerala-school (Mādhava-Nīlakaṇṭha) corrections","retrieved_at":"2026-05-14T11:45:51.099Z","verification":{"type":"multi-marker","confidence":"canonical"}}],"meta":{"generated_at":"2026-05-14T11:45:51.099Z","pillar_versions":{"BOB-History":"Pūrṇa"}}}