If some sort of breakthrough is not achieved by then, Israel will, for the first time in its political history, enter a period in which any MK is able to receive the mandate - or perhaps an equally unprecedented third round of elections within 12 months.
When this would play is something that no one knows as yet, but there are some questions that can be answered now.
Gantz has until the clock strikes midnight on Wednesday to inform the president whether he succeeded in forming a government.
At present, there are several possible scenarios for a government.
1. Unity government with Blue and White party and Likud, which some of the other parties in the right-wing bloc will join as laid out in President Reuven Rivlin's outline.
2. A minority government made up of Blue and White, Labor-Gesher, Democratic Union and Yisrael Beytenu, with the Joint List (of Arab parties) supporting the government from the outside.
3. A minority government made up only of Blue and White, Labor-Gesher and Yisrael Beytenu, with Democratic Union and the Joint List supporting from the outside.
A government needs the support of 61 of the 120 MKs, but not all parties supporting said government are obligated to join it.
A minority government consists of less than 61 MKs, with external support from opposition parties that align with the general values, but do not necessarily want to join.
Israel has had in its past several minority governments.
The first example is Yitzhak Rabin's second government in 1992, which it started with 62 MKs.
After a year, the ultra-Orthodox Shas party and its six lawmakers left the government over disagreements regarding religion and state affairs, leaving Rabin with a minority government.
The second example is in 2002, where the Labor-Meimad faction and its 26 MKs left Ariel Sharon's first government, leaving him with only 53 MKs.
If by midnight Wednesday Gantz can announce to Rivlin his success in formulating a government, the next step is to secure the Knesset approval by a vote in the plenum.
Knesset Speaker Yuli Edelstein will need to schedule a plenary meeting within a week in order to vote in the new government.
If the government does not receive a vote of confidence from at least 61 MKs, Israel moves into a 21-day period in which any MK can receive the mandate to form a government.
By law, 61 MKs can submit a joint petition to the president, recommending any MK to form a government, if that person agrees.
Any lawmaker is eligible for this recommendation, not just a party leader – even Gantz and Netanyahu, who have already had a try.
If 61 MKs agree on a new candidate, the president will hand them the mandate, beginning a lightning coalition formation process that lasts two weeks.
If after that option isn played out and 61 MKs cannot find a different candidate, elections place within 90 days.
By law, the elections will take place on a Tuesday no later than March 10, 2020.
Because this potential date coincides with the Purim holiday, it is possible that the elections will take place on March 3.
As in previous instances of early elections, the Knesset will have to disband itself by a vote a 61-MK majority to pass.