Dasami / Ekadasi / Dwadasi / Trayodasi

From Padma Puran:

Dashami + Ekadashi + Dwdashi all three make Harivasara or thithitrya.
On all these three days few things are restricted.

kamsyaM mAMsaM masArAMshca caNakAn kOdravAMsthatA
shAkaM madhu parAnnaMca punrbhOjana maiThunE
vaishNavO vrata kartAca dashamyAm dashavarJyayEt ||

"The following ten things should be given up on the Dashami, (the tenth
phase of the Moon), the day before the Ekadashi: 

1. eating on bell-metal plates, 
2. eating any kind of urad-dal, 
3. eating red-lentils, 
4. eating chick-peas, 
5. eating kondo (a kind of grain that resembles poppy seeds or agarpanthas seeds), 
6. eating spinach, 
7. eating honey, 
8. eating in another person's house/home, 
9. eating more than once and 
10. participating in sex of any kind.

dyUtaM krIDAMca nidrAMca tAMbUlaM daMtadhAvanaM
parApavAdaM paishunyaM stEyaM hiMsAM tathAratiM
khrOdhaM caiva anrataM vAkya mEkAdashyaM vivarjayEt||

"On the Ekadashi day one should give up the following eleven: 

1. eating on bell-metal plates
2. gambling, 
3. sports, 
4. sleeping during the daytime, 
5. beetal nuts and its leaf, 
6. brushing one's teeth, 
7. spreading rumours, 
8. faultfinding, 
9. talking to the spiritually fallen, 
10. anger and 
11. lying.

kAMsyaM mAMsaM surAM kshoudraM tailaM patita bhAshaNaM
vyAyAmaMca pravAsaMca punarbhOjana maithunaM
vraksha praShTaM masUrAnnaM dvAdashyAM parivarjayEt ||
"On the Dwadashi the day after Ekadashi (the twelfth phase of the Moon), one should give up the following twelve: 

1. eating on bell-metal plates, 
2. eating urad-dal, 
3. eating red-lentils,  
4. Drinking honey, 
5. lying, 
6. strenuous exercise, 
7. travel, 
8. eating more than once, 
9. any sexual activity, 
10. shaving the body,face or head, 
11. smearing oils on one's body and 
12. eating in another's home."

Source
Varuthini Ekadasi / Page / Vallabhacharya Jayanti
http://fa8t.blogspot.com/2013/05/varuthini-ekadasi-page-vallabhacharya.html

If you have observed a complete fast (meaning, you have not even taken water on Ekadasi day) you do not need to break the fast the following day with grains. You can break it with caranamrita (Krsna's foot bathing water) or fruit at the times mentioned herein.But if on Ekadasi you took fruit, vegetables, etc. then you should break it with grains next morning at the proper times listed for paran.

Since Shiva consumed Aalakala visham on the following day at twilight this event is called Pradosham or Trayodasi .

Trayodasi is Day After Dwadasi or Day After Tomorrow of Ekadasi

"Observe vrat(vow of worship) of Shiva always on Trayodashi" The Original Guru of Vaishnavas

Festival
http://shivadurga.blogspot.com/2010/12/lord-shiva-and-pradosh-vrat-or-fasts.html
Rest Place / Mount

https://freeglobaluniversity.blogspot.com/search/label/Snake