--svatantramasvantantraM cha dvividhaM tatvaMishyate--
--svatantro bhagavAn vishnuH--
Sri Madhvacharya, in his tatvasaMkhyAna
Notes on ekAdashi nirNaya
Culled by Shobha Srinivasan
Sadachara Vinodha book by Sri Vyasanakare Prabhanjanacharya
aruNodayakAle tu dashamI yadi dR^ishyate
na tatraikadashI kAryAh dharmakAmArthanAshinI
(padmapurANam.h (brahma khanda a 15 shloka 32)
Even if there is a trace of Dashami at the time of arunodaya, that ekadashi is considered as viddha ekadashi . The destruction of dharma & all purushArthas is incurred by a fast on such a day.
kshaye vA.apyathavA vR^iddhau sampRapte vA dinakshaye
upoShyA dvAdashI puNyA pUrvaviddhAM parityajeth
(KrishnAmruthamaharnava Sloka 121)
When there is thithi kshaya, thithi vriddhi & dinakshaya (when Dasami, Ekadashi & Dwadashi fall on the same day) in all these three situations, a fast should not be undertaken on Ekadashi which is Dashami viddha. A fast should be observed on Dwadashi.
Characteristics of Arunodaya (Daybreak)
chatartro gaTikAH prAtararuNodaya uchyate
yatInAM snAnakAlo.ayaM gaMgAMbhaH sadR^ishaH smR^itiH
(KrishnAmruthamaharnava sloka 131)
Four ghatikas before sunrise is considered as arunodaya. The shastras say that this time is as holy as the waters of the Ganga for ascetics to have their bath. (It means that a bath during arundodaya gives as merit as a bath in the Ganga).
What is Ghatika?
From HarikathAmruthasaara,
paramasUkShmavukShaNavayidhu thRuti karesuvadhu aivaththu
thruti lava veradu lavavu nimiSha nimiShagaLemtu mAthrayuga
gurudhashaprANArupaLa hanneradu bhANavu ghaLige
thrimshathi iruluhagaLaruvaththughatigaLahOrAthrigaLu || 23-56 ||
The smallest time unit is a moment;
5 kshana = Truti; 50 Truti = 1 lava; 2 lava = 1 minute; 8 minutes = a matra;
2 matra = a guru; 10 guru = prana; 6 prana = 1 pala; 60 pala = 1 Ghaika;
30 Gathikas = 1 day or night; 60 Ghathikas = a full day.
Ed.: There is something confusing in the above time divisions writeup, which I have not verified with the source. But, look here for a similar discussion (very nice, erudite and simple).
When Ekadashi is Dashami Viddha, a fast should be undertaken in Dwadashi.
putrarAjyavivR^id.hdhyarthaM dvAdasyAmupavAsanaM
tatra kratushataM puNyaM trayodashyAm tu pAraNam.h
(krishnAmruthamaharnava, Shloka 134)
When Ekadashi is Dashami viddha, a fast should be observed in Dwadashi & the fast broken parana on Thrayodashi. This brings prosperity for the country & progeny. One gets merit equal to the merit of performing hundreds of yajnas.
jn~AtvA viprA (prai) stithiM samyag.h daivajn~yaiH samudIritAM
kartavya upavAsastu anyathA narakaM vrajet.h
(KrishnAmruthamaharnava, sloka 120)
People should fast only on the day decided by persons well versed in Astrology. Otherwise the fast will lead to hell.
bahvAgamavirodhe tu brAhmaNeShu vivAdiShu
upoShyA dvAdashI puNyA pakshayorubhayorapi
(KrishnAmruthamaharnava Sloka 138)
If there are conflicting statements in the shastras regarding veda, when scholars express different opinions, it is meritorious to observe a fast on Dwadashi no matter which Ekadashi it is (either sukla or krishna paksha).
HARIVAASARA DURING DASHAMI & DWADASHI
ekAdashyAH prAMtabhAgo dvAdasyAH pUrva eva cha
harivAsaranAmA.asau sarvakAlottamaH smR^itaH
brahmAhatvA surApAnaM steyaM gurvaganAgamaH
tasminstu bhunjataH pApAnyekasthAni bhavaMtyutaH
(vishnuthIrtha sanyAptapaddati)
The last part of (dasami viddha) Ekadashi & the first part of Dwadashi thithi is also known as Harivasara (Haridina). This period is also auspicious & merits for fasting. If any food is taken during this period, it amounts to killing of brahmin (brahma hathya) & others such sins (so if there is Harivasara on Dashami, food should be taken before Harivasara begins & if there is Harivasara on Dwadashi, the fast should be broken only after Harivasara is over.