Lazenby (1998) p. 276, Appendix III The Diary of the March, sets a precise hypothetical schedule of Hannibal's march.
The precision exceeds that of the evidence, but it is based on a synoptic view.
The date given is September 25 for the main crossing and battle.
All dates for the battle are pinned on a statement by Polybius in Histories III.54 that Hannibal reached the top of the pass about the setting of the Pleiades, which Lazenby takes to be "the first fortnight in November" and sets arbitrarily at November 1 in the Diary.
Counting back the estimated time for events he arrives at September 25 for the crossing.

Lazenby (1998) p. 31, based on the 160 + 60 that transported Roman troops in 218 mentioned in Polybius Histories III.41.
Livy on the other hand says the Senate voted the launching of 225 banked ships and 20 light galleys, History of Rome XXI.17.

Livy History of Rome XXI.17.

Titus Livius. "
Livy's History of Rome".
J. M. Dent & Sons, Ltd., London, 1905.
p. 21.26.
Retrieved 30 October 2015.

Peddie (2005) p. 14
Lazenby (1998) p. 32
Lazenby (1998) p. 33, from Appian Hannibalic War 1.4.

Peddie (2005) p. 18
Goldsworthy (2003) p. 160
Ernle Bradford, Hannibal, Open Road Media, 2014
Livy 21: 27
Cottrell (1992) p. 44
Lazenby (1998) p. 35
Lancel (1999) p. 68
Lazenby (1998) pp.
32-33
Goldsworthy (2003) pp.
159 & 167
Bagnall (1990) p. 160
Lazenby (1998) p. 34
Delbruck (1990) p. 364
Lazenby (1998) p. 276, Appendix III The Diary of the March, sets a precise hypothetical schedule of Hannibal's march. The precision exceeds that of the evidence, but it is based on a synoptic view. The date given is September 25 for the main crossing and battle. All dates for the battle are pinned on a statement by Polybius in Histories III.54 that Hannibal reached the top of the pass about the setting of the Pleiades, which Lazenby takes to be "the first fortnight in November" and sets arbitrarily at November 1 in the Diary. Counting back the estimated time for events he arrives at September 25 for the crossing.
Lazenby (1998) p. 31, based on the 160 + 60 that transported Roman troops in 218 mentioned in Polybius Histories III.41. Livy on the other hand says the Senate voted the launching of 225 banked ships and 20 light galleys, History of Rome XXI.17.
Livy History of Rome XXI.17.
Titus Livius. "Livy's History of Rome". J. M. Dent & Sons, Ltd., London, 1905. p. 21.26. Retrieved 30 October 2015.
Peddie (2005) p. 14
Lazenby (1998) p. 32
Lazenby (1998) p. 33, from Appian Hannibalic War 1.4.
Peddie (2005) p. 18
Goldsworthy (2003) p. 160
Ernle Bradford, Hannibal, Open Road Media, 2014
Livy 21: 27
Cottrell (1992) p. 44
Lazenby (1998) p. 35
Lancel (1999) p. 68
Lazenby (1998) pp. 32-33
Goldsworthy (2003) pp. 159 & 167
Bagnall (1990) p. 160
Lazenby (1998) p. 34
Delbruck (1990) p. 364
Battle of Rhone Crossing