OPINION
Michael Gresser sued Calvin and Cheryl Hotzler for specific performance of a purchase agreement for commercial real estate and, alternatively, for breach of contract. On the Hotzlers’ motion for partial summary judgment on Gresser’s specific-performance claim, the district court held that the purchase agreement was invalid and entered final judgment against Gres-ser pursuant to Minn. R. Civ. P. 54.02, dismissing both the specific-performance and breach-of-contract claims. Gresser appeals from the judgment.
FACTS
The property in dispute includes five acres of land and a building that formerly housed the Stagecoach Theatre in Shako-pee. In early 1998, Michael Gresser, a real estate investor, began' negotiating with landowners Calvin and Cheryl Hot-zler to purchase the property. In July, Gresser submitted to the Hotzlers an unsigned, proposed purchase agreement that, among other items, required the Hotzlers *382 to deliver a recertified survey on August 10, 1998, and provided for closing on September 1, 1998. The Hotzlers changed several terms, initialed the changes, signed the purchase agreement, and returned it to Gresser’s attorney on August 4,1998.
On August 10, 1998, Gresser initialed the Hotzlers’ changes and signed the purchase agreement. Gresser, however, made two additional changes. He changed the survey delivery date to September 10, 1998, and the closing date to October 15, 1998. Gresser initialed both date changes. Gresser made these changes on the advice of his attorney, who had talked to the Hotzlers’ realtor. The attorney and the realtor agreed that, because of the time that had elapsed, the original survey and closing dates had become impractical. The attorney knew that the realtor had not consulted the Hotzlers about the changes, and both Gresser and his attorney knew that the realtor did not have the power to bind the Hotzlers.
Gresser’s attorney returned the signed purchase agreement to the realtor on August 12, 1998, along with $2,000 earnest money. Gresser and his attorney expected that the Hotzlers would initial the date changes and return the purchase agreement to them. The realtor delivered the purchase agreement to Calvin Hotzler on August 12, 1998, but testified that he did not indicate whether Gresser had signed the counteroffer. Calvin Hotzler assumed the parties had a deal, but he did not read the purchase agreement. Instead, he placed it on the kitchen counter to await the return of Cheryl Hotzler, who was out of town. Later that day, Calvin Hotzler showed Gresser the property and introduced him to tenants as the buyer.
On the afternoon of August 12, 1998, the realtor received another offer for the property, which he forwarded to the Hotzlers. Calvin Hotzler placed this document on the kitchen counter as well. On August 13, the Hotzlers reviewed both documents, decided to accept the new offer, and signed that purchase agreement.
ISSUES
I. Given the undisputed facts in the record, did the district court err by concluding that the purchase agreement between the Hotzlers and Gresser was not legally binding?
II. Did the district court err by refusing to apply equitable estoppel?
ANALYSIS
On appeal from summary judgment, the reviewing court determines whether any genuine issues of material fact exist and whether the district court erred in its application of the law.
Wallin v. Letourneau,
I
Whether a contract is formed is judged by the objective conduct of the parties and not their subjective intent.
Cederstrand v. Lutheran Bhd.,
Gresser first argues the district court erred by making findings on disputed facts material to whether the parties formed a contract. We disagree. The district court’s function on a summary judgment motion is to determine whether genuine factual issues exist.
DLH,
Gresser primarily argues that his changes to the purchase agreement are within the modification exception to the mirror-image rule because he unconditionally accepted the Hotzlers’ counteroffer and merely suggested the date changes. According to Gresser, he accepted unconditionally because he would have been willing to comply with the original dates, the realtor encouraged Gresser to make the changes, and Calvin Hotzler introduced Gresser as the owner of the property on August 12.
Viewed objectively, these facts do not demonstrate that Gresser positively accepted the purchase agreement. First, Gresser’s uncommunieated subjective intent is not relevant, and, second, these facts do not suggest that the Hotzlers knew or should have known that Gresser offered the change in dates only as a suggestion. To the contrary, the undisputed facts regarding absence of any express communication, the method of initialing the changes, and the prior course of dealings between the parties indicate that the changes were part of the series of counteroffers.
Minnesota has applied the modification exception sparingly and only to those cases in which objective manifestations of acceptance existed separately from the suggestions for modifications.
See Podany, 235
Minn. at 38,
Gresser alternatively argues that his changes to the purchase agreement did not preclude contract formation because the changes were immaterial. The mirror-image rule historically has been strictly construed to forbid even minor variations between offer and acceptance. Many modern courts have relaxed the rule, holding that only an acceptance that differs
materially
from the terms of the original offer prevents contract formation.
See, e.g., Raydon Exploration, Inc. v. Ladd,
The corollary to this modern rule is that an immaterial variation in the acceptance does not impede contract formation. For instance, several courts have held that, under this exception, variations im
*384
plied in the offer do not interfere with the completed contract.
Northwest Television Club,
The Minnesota Supreme Court used the language of the immateriality exception in
Markmann v. H.A. Bruntjen Co.,
“Authority on what constitutes a material variation-is meager.”
Northwest Television Club,
Under this principle, the date changes Gresser made are material. The changes directly affect Gresser’s performance obligations under the contract, postponing his duty to perform by almost six weeks. The law of contracts is not advanced by allowing a contracting party to manipulate the finality of an obligation by rejecting an insubstantial change, but few terms are more important to sellers of real estate than the date on which they will receive the purchase money. The purchase agreement’s inclusion of a time-is-of-the-essence clause further evidences the materiality of the performance date. As a matter of law, the exception to the mirror-image rule for immaterial variations does not apply to the changes Gresser made to the purchase agreement.
In retrospect, Gresser may have been very willing to expressly note that the changed dates were proposals rather than conditions or to retain the earlier closing date rather than risk the loss of the property. But contract formation proceeds on an objective basis and courts should not reconstruct, much less call back, the written word. The high volume of real estate transactions in Minnesota reinforces the importance of identifying and preserving a bright line in the formation of purchase agreements.
*385 II
The district court rejected Gres-ser’s argument that the Hotzlers should be equitably estopped from denying the validity of the purchase agreement. We note at the outset that “it is questionable whether a contract can be created in the first instance by estoppel.”
St. Paul Fire & Marine Ins. Co. v. Bierwerth,
Equitable estoppel arises when “one by his acts or representations, or by his silence when he ought to speak, intentionally or through culpable negligence, induces another to believe certain facts to exist, and such other rightfully acts on the belief so induced in such a matter that if the former is permitted to deny the existence of the facts it will prejudice the latter.”
Transamerica Ins. Group v. Paul,
The general rule is that real estate agents have no implied authority to contract on behalf of their principals.
La Plant v. Loveland,
We also reject Gresser’s argument that any deficiencies in the proof of implied or apparent authority were cured by ratification when Hotzler introduced Gresser as the buyer of the property after receiving the purchase agreement with the changed dates. “Ratification occurs when one having full knowledge of all material facts confirms, approves or sanctions a previous act done on behalf of the principal without authority.”
Centennial Ins. Co. v. Zylberberg,
The record does not support Gresser’s claim that Hotzler had actual notice of the changes to the contract when he showed Gresser the property and introduced him as the buyer.
See Jackson v. Badger,
Finally, ratification “must be by an act of the character required for the original authority.”
Judd v. Arnold,
Gresser’s equitable estoppel claim also fails on the essential element of reasonable reliance.
See Transamerica,
DECISION
Because the date changes to the purchase agreement precluded contract formation as a matter of law, and because Gresser failed to assert facts sufficient to support an equitable estoppel claim, the district court properly granted summary judgment to the Hotzlers.
Affirmed.
