Gemara

(Rav Nachman): If Reuven and Shimon each claimed 'I inherited this land (or ship) from my fathers', Kol d'Alim Gavar.

Question: Why is this different than two documents with the same date?

(Rav): If two documents have the same date, the bearers split the property.

(Shmuel): We apply Shuda (it is left to the judges' discretion).

Kesuvos 93b: Rav holds like R. Meir, who says that Edei Chasimah (the witnesses who sign on a document) Karsei (empower it. Therefore, it does not matter which was given first.) Shmuel holds like R. Elazar, who says that Edei Mesirah (the witnesses who see a document given to the recipient) Karsei. (Therefore, the first one given is valid.)

Answer: There, we will never know which document was given first. Here, perhaps one will bring witnesses later (we do not want to give a ruling that might be overturned later).

Kesuvos 93b (Mishnah): If all the Kesuvos have the same date, whichever comes first, even by an hour, collects first. In Yerushalayim they used to write the hour. If all have the same hour and there is only 100 in the estate, they share it equally.

94b: Rami bar Chama's mother wrote her property to him in the morning. In the afternoon, she wrote it to Mar Ukva bar Chama. Rami went to Rav Sheshes, who ruled that Rami bar Chama receives the property. Mar Ukva bar Chama went to Rav Nachman, and he ruled in his favor.

Rav Sheshes: I ruled in favor of Rami because his document was written first.

Rav Nachman: We care which document was written earlier in the day only in Yerushalayim (where they write the hour in the document)! The Halachah is Shuda. I ruled based on my estimation (or preference).

Rishonim

Rif and Rosh (Kesuvos 53b and 10:13): Rav and Shmuel discuss documents for land, e.g. purchases or gifts. If they were admissions or loans, a Mishnah (93b) teaches that they divide the money.

Rebuttal (Ran DH Aval Beis): Perhaps Shuda applies even to loans. The Stam Mishnah is R. Meir, therefore it says they divide! Also, the Mishnah does not discuss Shuda at all. It teaches only how to divide, e.g. in a case when all agree that Shuda does not apply and they divide, e.g. they are for the same hour, or a Shali'ach acquired at once for many recipients!

Rosh (ibid.): If two loan documents have the same date, they divide, for both liens begin at the beginning of the day after the date, since the document does not prove that it starts before this. Knyanim take effect immediately. The first one acquired totally.

Hagahos Ashri: R. Baruch says that even though the Halachah follows Shmuel against Rav in monetary matters, here the Halachah follows Rav because we hold that when there is a doubt, we divide the money. The Yerushalmi says that the Mishnah of three Kesuvos opposes Shmuel.

Rif and Rosh (Kesuvos 45b and 9:11): Regarding sales and gifts, the Halachah follows Shmuel (Shuda). In Bava Basra (34b), Rav Nachman taught about two people who claim 'I inherited this from my fathers', the law is unlike two documents with the same date. We answered that there, we will never know which document was given first. We asked why Rav Nachman's law is different than we do not know whether a cow for slave gave birth before or after it was sold. We answered that there, each has Drara d'Mamona. In Rav Nachman's case, it belongs absolutely to one or the other. We did not give this answer regarding two documents. This shows that regarding two documents, there is not Drara d'Mamona for both. Rather, it belongs to one or the other. This shows that it cannot refer to loan documents.

Rif: The case of Rami bar Chama's mother was a gift through a document alone, without Kinyan (Chalipin). Had there been a Kinyan, all would agree that the first recipient receives it.

Rif (Gitin 47a): The Halachah follows R. Elazar for Gitin.

Question (Ran): The Rif rules like R. Meir for monetary documents. However, regarding Shuda he rules like Shmuel, who rules like R. Elazar!

Answer (Sefer ha'Zechus): The Gemara said that R. Meir would not say Shuda. This is like the opinion that says that witnesses acquire on behalf of the recipient when they sign. Shmuel holds like this. Since the signatures take effect the same moment (the end of the day), it is as if both recipients acquired together, even if one received the document first. We hold that one does not acquire through the signatures, rather, until he gets the document. Therefore, Shuda applies even according to R. Meir. Another prrof is that R. Meir agrees that if one wrote and gave a document, if he writes and gives another document the same the day, the latter is Batel. Since it is possible that this happened, Shuda applies.

Rebuttal (Ran): There is no proof that Shmuel holds that one acquires through the signatures. We learn from Bava Metzia that he disagrees! If Shmuel could say Shuda even though he holds like R. Meir, what forced the Gemara to say that he says Shuda, like R. Elazar? Do not say that it is because Shmuel rules like R. Elazar. If we could establish Shmuel even like R. Meir, we would, to teach about a case when there were no Kosher Edei Mesirah! (R. Elazar agrees that then it is Kosher due to the Edei Chasimah.) According to R. Meir, even if one gave one document first, since he did not write the hour to clarify this, he made the Kinyan incomplete. It is complete only from when it is clear from the document, i.e. the end of the day. This is the same for both!

Hagahah: The Gemara suggested that Shmuel holds that one acquires through the signatures, and never proved otherwise. This shows that it is feasible to say so!

Rambam (Hilchos Zechiyah 5:6): If there are two sale or gift documents for a field, and the dates are the same, if it is not the practice to write the hour on the document, it is left to the judges' discretion. Whomever they lean to leave the field with, he keeps it.

Rambam (7): This is when there is no Kinyan in the document; the field was acquired through the document. We do not know who received it first. If there is a Kinyan, whoever made the Kinyan first gets the field. We would ask the witnesses. Similarly, if witnesses say that one of them got the document first, he gets the field.

Mordechai (Bava Metzia 1:255): If David wrote to Levi in the morning and to Moshe in the afternoon and Moshe's document was given before Levi's, Moshe acquires. Witnesses acquire for the recipient (from when they sign) only if it is evident from the document that it was first. When we do not know which was given first, we use Shuda, even if we know which was written first.

Poskim

Shulchan Aruch (CM 240:3): If there are two sale or gift documents for a field, and the dates are the same, if it is not the practice to write the hour on the document, it is left to the judges' discretion. Whomever they lean to leave the field with, he keeps it.

Beis Yosef (DH u'Mah she'Chosav v'Eino): The Tur says that we do not know which document was given first. He means, if one was given at least a day earlier. If they were given the same day, it does not matter which was given first, like Rav Nachman said (Kesuvos 94b).