delivered the opinion of the court:
This appeal arises from a post-decree order of the Circuit Court of Warren County which modified a decree of divorce changing the custody of the one minor child of the marriage from his mother to his father. The plaintiff-petitioner, Donnie E. Sexton, was divorced from the defendant, Janice S. Sexton on August 10, 1976.
The sole issue presented on appeal is whether the judgment changing custody from the defendant to the plaintiff is against the manifest weight of the evidence. We have examined the record in this case and have determined that an error occurred in the trial court which prevents us from considering the issue raised on appeal on its merits. Because the . error we recognize is essentially one of procedure no detailed recitation of the factual background is necessary.
As aforesaid, the record reflects that the parties were divorced on August 10, 1976, and no appeal was taken therefrom. The plaintiff subsequently, on April 25, 1977, filed the petition to modify the divorce decree to obtain custody of the child. Thereafter the Illinois Marriage and Dissolution of Marriage Act (Ill. Rev. Stat. 1977, ch. 40, par. 101 et seq.), hereinafter referred to as the Act, became effective on October 1, 1977. Following a hearing on the petition to modify, to change custody, on June 20, 1978, the trial court granted the child-custody change.
The application of the Illinois Marriage and Dissolution of Marriage Act to matters of substance pending on the effective date of the Act is well settled. (Kujawinski v. Kujawinski (1978), 71 Ill. 2d 563, 376 N.E.2d 1382; West v. West (1978), 62 Ill. App. 3d 963, rev’d on other grounds (1979), 76 Ill. 2d 226, 390 N.E.2d 880.) In the instant appeal the hearing on the issue of the petition to modify the original child-custody provisions of the divorce decree was not had until well after the new act became effective. Accordingly we conclude that the provisions of the Illinois Marriage and Dissolution of Marriage Act were applicable.
Whereas the old Divorce Act (Ill. Rev. Stat. 1975, ch. 40, pars. 1 through 21.4) did not contain any time limitation regarding the modification of child-custody orders because under the old act custody orders were modifiable as often as the parties desired if the required *484substantive grounds were otherwise established, section 610(a) of the new act provides:
“No motion to modify a custody judgment may be made earlier than 2 years after its date, unless the court permits it to be made on the basis of affidavits that there is a reason to believe the child’s present environment may endanger seriously his physical, mental, moral or emotional health.” (Ill. Rev. Stat. 1977, ch. 40, par. 610(a).)
The lapse of time between the original divorce decree including its order of custody to the defendant mother on August 10, 1976, and the order changing custody on June 20, 1978, clearly falls short of the two-year provisions of section 610(a) of the Marriage and Dissolution of Marriage Act (Ill. Rev. Stat. 1977, ch. 40, par. 610(a)). Our examination of the record reveals that no motion for leave to file a petition to modify the child custody or accompanying affidavits that the child’s present environment endangered seriously his physical, mental, moral or emotional health were filed by the plaintiff husband. Although a reviewing court should not normally search the record for errors which are not argued and not briefed, an exception exists for jurisdictional defects. (Saldana v. Wirtz Cartage Co. (1978), 74 Ill. 2d 379, 385 N.E.2d 664). We believe the provisions requiring leave of the trial court based upon proper affidavits set forth in section 601(a) of the Marriage and Dissolution of Marriage Act (111. Rev. Stat. 1977, ch. 40, par. 601(a)), to be mandatory and jurisdictional, and that the trial court erred in this case by proceeding on the merits of the petition to change the child custody within two years of the original divorce decree award of child custody absent compliance with the new act.
Though generally the use of the words “may” and “shall” when used in context of a statute can be used interchangeably as will best express the legislative intent of the drafters of the particular statute:
“It has been stated as a rule of construction that ‘the word “may” in a statute will be construed to mean “shall” whenever the rights of the public or third persons depend upon the exercise of the power of performance of the duty to which it refers, and such is its meaning in all cases where the public interest and rights are concerned, or a public duty is imposed upon public officers, and the public or third persons have a claim de jure that the power shall be exercised,’ or where it is necessary to construe it to carry out the intent of the legislature.” Figures v. Swank (1970), 128 Ill. App. 2d 211, 216, 263 N.E.2d 599, quoting Brokaw v. Commissioners of Highways (1889), 130 Ill. 482, 490, 22 N.E. 596.
Recent interpretations of the new Illinois Marriage and Dissolution of *485Marriage Act have consistently held its provisions to be mandatory in its application rather than directory. (See Strukoff v. Strukoff (1979), 76 Ill. 2d 53, 389 N.E.2d 1170 (construing Ill. Rev. Stat. 1977, ch. 40, par. 403(a)(3)), and DeYoung v. DeYoung (1978), 62 Ill. App. 3d 837, 379 N.E.2d 396 (construing Ill. Rev. Stat. 1977, ch. 40, par. 604(a)). We believe our reading of the word “may” in section 610(a) of the Act (Ill. Rev. Stat. 1977, ch. 40, par. 610(a)) as mandatory to be consistent with the rules of statutory construction established by Illinois courts.
Further, a statute adopted by Illinois from another State will be presumed to have been adopted with the construction placed upon it by that State before its adoption by Illinois (People v. Moczek (1950), 407 Ill. 2d 373, 395 N.E.2d 429). The Illinois Marriage and Dissolution of Marriage Act is no exception to this rule. In In re Custody of Mueller (1979), 76 Ill. App. 3d 860, 395 N.E.2d 677, the Fifth District Appellate Court construed the language of section 610(a) of the Illinois Marriage and Dissolution of Marriage Act (Ill. Rev. Stat. 1977, ch. 40, par. 610(a)), which is modeled after section 409(a) of the Uniform Marriage and Divorce Act, and approvingly cited cases from other jurisdictions which had also adopted the Uniform Act. Accordingly we note that section 409(a) of the Uniform Act has been construed to be mandatory and jurisdictional in In re Custody of Dallenger (Mont. 1977),_Mont__, 568 P.2d 169; Holm v. Holm (1977), 172 Mont. 81, 560 P.2d 905; and Robbins v. King (Ky. 1975), 519 S.W.2d 839. See also Ronchetto v. Ronchetto (1977),_Mont._, 567 P.2d 456; Schiele v. Sager (1977), _Mont._, 571 P.2d 1142; In re Marriage of Harris (Colo. 1975), 543 P.2d 1286; Manson v. Manson (Colo. App. 1974), 529 P.2d 1345; Richards v. Superior Court (1974), 22 Ariz. App. 66, 523 P.2d 117; and Commissioner’s Note, 9A Uniform Laws Annotated §410, Uniform Marriage and Divorce Act (1973).
Equally as important as the interpretation given by various courts in Illinois and other jurisdictions to section 610(a) in our resolution of this case is an examination of the intent of the General Assembly in adopting that particular provision. Section 102 of the Marriage and Dissolution of Marriage Act (Ill. Rev. Stat. 1977, ch. 40, par. 102) sets forth the purposes which we believe are controlling in interpreting the legislative intent of section 610(a) of the Act:
“This Act shall be liberally construed and applied to promote its underlying purposes which are to:
e # #
(2) strengthen and preserve the integrity of marriage and safeguard family relationships;
*486(4) mitigate the potential harm to the spouses and their children caused by the process of legal dissolution of marriage;
(5) make reasonable provision for spouses and.minor children during and after litigation.” (Ill. Rev. Stat. 1977, ch. 40, par. 102(2) (4) (5).)
In the recent case of In re Custody of Harne (1979), 77 Ill. 2d 414, 420, 396 N.E.2d 499, the supreme court quoted with approval the commissioners’ note to section 409 of the Uniform Marriage and Divorce Act:
“ ‘Most experts who have spoken to the problems of post-divorce adjustment of children believe that insuring the decree’s finality is more important than determining which parent should be the custodian. See Watson, The Children of Armagedon: Problems of Custody Following Divorce, 21 Syracuse L. Rev. 55 (1969).’ ”
The court then went on to say:
“The policy evident in the commissioners’ notes is also apparent in the provision of section 610(a) that ‘[n]o motion to modify a custody judgment may be made earlier than 2 years after its date, unless the court permits it to be made on the basis of affidavits that there is reason to believe the child’s present environment may endanger seriously his physical, mental, moral or emotional health.’ (Ill. Rev. Stat. 1977, ch. 40, par. 610(a).) The aversion to custody changes is further manifested by the requirement in section 610(b) that the custodian previously appointed shall be retained absent the conditions specified in sections 610(b) (1), (2) or (3). By creating a presumption in favor of the present custodian, the legislature has sought to promote a stability and continuity in the child’s custodial and environmental relationships which is not to be lightly overturned.” 77 Ill. 2d 414, 420-21, 396 N.E.2d 499, 502.
We believe, as did the supreme court in Harne, that our present two-year moratorium on child-custody change is designed to prevent repeated and unsubstantial petitions for modification of the decree of marriage dissolution as to child custody. It discourages the noncustodial parent from trying to punish a former spouse by frequent and unfounded attempts to modify the prior custody order by requiring the movant for a custody change within two years of a prior custody order to show a much greater urgency for the custody change than the usual standard of the child’s best interests. This provision fosters custodial continuity for the child and still allows for an immediate custody change where an emergency situation in the child’s present environment arises which endangers his physical, mental, moral or emotional health. The two-year limitation period on modifying child custody orders was an obvious attempt of the legislature to mitigate the harm to the children of the *487marriage legally dissolved by affording maintenance of family stability. The minor child is generally assured of a minimum of two years of custodial continuity, which lessens the effect of the disruption of family life by the dissolution of the marriage and safeguards the new existing family relationship. “Repeated efforts for modification of the decree are looked on with disfavor by the courts, and there should be an end to the constant changes and modifications of orders having to do with the custody of a child.” (27B C.J.S. Divorce §317(1), at 528 (1959).) That finality and security be afforded to the minor child of a dissolved marriage is the obvious desired end result.
Although it could be argued in cases such as this that custody ordered by the trial court might be upset by deciding as we do, such an argument fails to recognize, however, the authority of the trial court as well as this court to stay the trial court order as to custody (Ill. Rev. Stat. 1977, ch. 110A, par. 305(b)). It should be noted that in the case before us the record does not reflect whether the order changing custody from the mother to the father has been accomplished.
As was aptly stated in Robbins v. King (Ky. 1975), 519 S.W.2d 839, 840, “The statute unequivocally requires that the motion [to change child custody] be denied unless the court finds that adequate cause for a hearing has been established by the affidavits. As there were no affidavits filed, the court had nothing to consider and was therefore required to forthwith deny the motion.” We hold that a trial court cannot, within a two year period following a custody judgment, jurisdictionally entertain a request to modify the prior custody judgment in the absence of a motion accompanied by affidavits in compliance with section 610(a) of the Act which affidavits have convinced the trial court that the minor child’s present custodial environment presents some emergency danger to the minor child. Several recent Illinois cases have by implication approved of a mandatory reading of section 610(a) consistent with the views we express today. See In re Marriage of Farris (1979), 69 Ill. App. 3d 1042, 388 N.E.2d 232; Boggs v. Boggs (1978), 65 Ill. App. 3d 965, 383 N.E.2d 9; and DeFranco v. DeFranco (1978), 67 Ill. App. 3d 760, 384 N.E.2d 997.
The trial court failed to apply section 610(a) of the Act to the instant case. As we construe the requirements of section 610(a) of the Act to be mandatory and jurisdictional, reversible error occurred when the trial court in the instant case failed to comply with section 610(a) of the Act and instead proceeded to a hearing on the merits of the petition to modify the decree to change child custody. Therefore, we will not make a determination of whether the manifest weight of the evidence supports the order of the trial court changing the custody of the child as said order should not have been entered.
*488For the reasons stated the judgment of the Circuit Court of Warren County is reversed.
Judgment reversed.
STENGEL, J., concurs.