OPINION
COATS, Chief Judge.In Blakely v. Washington,1 the United States Supreme Court held that “[a]ny fact (other than a prior conviction) which is necessary to support a sentence exceeding the maximum authorized by the facts established by a plea of guilty or a jury verdict must be admitted by the defendant or proved to a jury beyond a reasonable doubt.”2 Avery, who had been sentenced -by Acting Superior Court Judge Jane F. Kauvar before the Blakely decision, filed a motion to correct his sentence under Alaska Criminal Rule 35(a), arguing that his sentence was illegal under Blakely because Judge Kauvar had found several aggravating factors without submitting those aggravators to a jury. Judge Kauvar concluded that she should review Avery’s sentence. The State argued that Judge Kauvar had no authority to review Avery’s sentence because all of the aggravating factors that the court had previously found were based upon Avery’s prior convictions, and therefore, Blakely did not require submission of these aggravating factors to a jury. When Judge Kauvar set a sentencing hearing to review Avery’s sentence, the State filed a petition for review in this court. We granted the petition. We now conclude that all of the aggravating factors that applied to Avery’s sentence were based upon his prior convictions, and therefore, Blakely did not require jury submission.
On appeal, Avery raises a new issue which he did not present in the trial court. Avery argues that this prior conviction exception to Blakely relies on questionable authority— Almendárez-Torres v. United States.3 He urges us to anticipate that the Supreme Court will overturn Almendárez-Torres and hold that the government must prove any prior conviction that increases a defendant’s maximum sentence to a jury beyond a reasonable doubt. In a related argument, Avery argues that, under Alaska law, the aggravating factors in his case, even if they *961were based upon his prior convictions, were elements of his offense. He argues that the State had to obtain an indictment from a grand jury and prove those aggravating factors to a jury beyond a reasonable doubt. We decline to reach these arguments because they were never presented in the trial court or raised in the petition.
Factual and 'procedural background
Lawrence Avery was convicted of misconduct involving a controlled substance in the fourth degree, a class C felony, for possession of cocaine.4 Avery was a third-felony offender for purposes of presumptive sentencing and therefore faced a presumptive term of 3 years imprisonment.5 Under Alaska’s pre-2005 presumptive sentencing laws, the State proposed four aggravating factors: (1) AS 12.55.155(c)(7) (“a prior felony conviction considered for the purpose of invoking the presumptive terms of this chapter was of a more serious class of offense than the present offense”); (2) AS 12.55.155(c)(8) (“the defendant’s prior criminal history includes conduct involving aggravated or repeated instances of assaultive behavior”); (3) AS 12.55.155(c)(15) (“the defendant has three or more prior felony convictions”); and (4) AS 12.55.155(c)(21) (“the defendant has a criminal history of repeated instances of conduct violative of criminal laws, whether punishable as felonies or misdemeanors, similar in nature to the offense for which the defendant is being sentenced under this section”).
Avery did not dispute his prior convictions or the applicable aggravating factors. Judge Kauvar found all four of the aggravating factors and sentenced Avery to the presumptive 3-year term, and based upon the aggravating factors, to an additional 1-year of suspended incarceration. Avery appealed his conviction to this court. We affirmed.6
Avery then filed a motion under Criminal Rule 35(a) arguing that Blakely made his sentence illegal. In Blakely, the Supreme Court held: “Any fact (other than a prior conviction) which is necessary to support a sentence exceeding the maximum authorized by the facts established by a plea of guilty or a jury verdict must be admitted by the defendant or proved to a jury beyond a reasonable doubt.”7 Avery argued that, under Blakely, which was decided after Judge Kau-var imposed the sentence, the maximum sentence for his crime was 3 years of imprisonment. He argued that Judge Kauvar could not lawfully find the aggravating factors without giving him the opportunity to contest those aggravating factors in a jury trial. In opposition, the State raised several arguments that Avery’s sentence was not illegal under Blakely.
Judge Kauvar concluded that, because at least some of Avery’s aggravating factors were based upon his prior convictions, she had the authority to impose an enhanced sentence under Blakely. But she concluded that she should conduct another sentencing hearing and evaluate whether, given the Blakely decision, she should impose the same sentence.
The State filed a motion for reconsideration, which Judge Kauvar denied. The State then filed a petition for review with this court, requesting a stay of the resentencing hearing pending resolution of the petition. In its petition, the State contended that Blakely did not make Avery’s sentence illegal. Therefore, the State argued that Judge Kauvar had no authority to modify Avery’s sentence.
We granted the petition and ordered briefing. We now conclude that all of the aggravating factors that Judge Kauvar found were based only upon Avery’s prior convictions, and there were no factual issues that Blakely would require a jury to determine. Therefore, Avery’s sentence was not illegal under Blakely for Criminal Rule 35 purposes and Judge Kauvar lacked authority to modify his sentence.
*962 All of the aggravating factors were properly based on Avery’s prior convictions
In Milligrock v. State,8 we stated:
Blakely expressly exempts a defendant’s prior convictions from the requirement of jury trial. That is, when a defendant’s prior conviction is the fact that authorizes a sentencing judge to exceed an otherwise applicable sentencing limit, the sentencing judge can rely on that prior conviction despite the normal Blakely requirement of a jury trial.9
Avery appears to concede that, under our prior decisions, he was not entitled to a jury trial on any of the aggravating factors because those aggravating factors were based upon his prior convictions.10
We agree with Avery’s concession. The first aggravating factor that Judge Kauvar found was that “a prior felony conviction considered for purposes of invoking the presumptive terms of this chapter was of a more serious class of offense than the present offense.” 11 We previously addressed this aggravating factor in Milligrock. We stated:
Aggravator (c)(7) — that one of the defendant’s prior felonies is of a more serious class than the defendant’s current offense — is expressly based on a defendant’s prior convictions. Assuming that there is no dispute as to the existence of those prior felony convictions, this aggravator presents no problem under Blakely.[12]
In the present case, Avery faced sentencing for a class C felony. It is uncontested that Avery had a prior conviction for a class B felony offense. The aggravator was therefore clearly established, and under Blakely, Avery was not entitled to a jury trial.
The next aggravating factor in question was that Avery had a history of aggravated or repeated instances of assaultive behavior. Avery concedes that, in Milligrock, we concluded that where the defendant has two or more convictions for assault, this aggravator has been established.13 It is uncontested that Avery had four prior convictions for assault. The aggravator was established based only upon Avery’s prior convictions. Therefore, Judge Kauvar did not violate Blakely in finding this aggravating factor without submitting it to the jury.
We next turn to aggravator (c)(15) (the defendant has three or more prior felony convictions). It is uneontested that Avery had three or more prior felony convictions. In order to find this aggravating factor, all Judge Kauvar had to do was count the prior felonies. There was no question for the jury to decide under Blakely. We accordingly conclude that this aggravating factor was clearly established and that Judge Kauvar did not violate Blakely in finding the aggravating factor without submitting it to the jury.
We turn next to the fourth aggravating factor, AS 12.55.155(c)(21) — that Avery had a history of repeated instances of criminal conduct similar in nature to his present offense. This aggravator poses a potential Blakely problem because it does not necessarily require proof that the prior instances of criminal conduct led to convictions. And even when proof of this aggravator is based on prior convictions, there might conceivably be a factual dispute as to whether the conviction represented conduct similar in nature to the defendant’s present offense (as opposed to a legal dispute as to whether given conduct was sufficiently “similar” for purposes of this aggravator).
In Milligrock, we pointed out a similar problem with respect to aggravator (e)(8)— that a defendant has a history of repeated instances of assaultive behavior. In particular, we pointed out that this aggravator presented a Blakely problem to the extent that it might be proved by instances of assaultive behavior that did not result in convictions for *963assault.14 But we concluded that proof of this aggravator based on prior convictions for assault does not violate Blakely.
In Grohs v. State,15 we directly addressed aggravator (c)(21) (criminal history of similar conduct).16 We held that, at least when a defendant did not dispute the existence of the prior convictions, “and when the State relied simply on the convictions themselves and the legal elements of those crimes, rather than attempting to introduce evidence of the particular facts underlying the prior convictions” the court could find the aggravator without violating Blakely.17 It is uncontested that Avery had several prior felony convictions for possession and sale of illegal drugs. Therefore, these convictions clearly established aggravator (e)(21), and there was no issue for a jury to resolve.
Judge Kauvar has no authority to modify Avery’s sentence
Criminal Rule 35(a) allows a court to “correct an illegal sentence at any time.” But, as our prior analysis demonstrates, there was nothing illegal about Avery’s sentence.
Criminal Rule 35(b) authorizes a court to “modify or reduce a sentence within 180 days of the distribution of the written judgment upon a motion made in the original criminal case.” Under Criminal Rule 53, a court does have the authority to relax the 180-day deadline if there is a showing of manifest injustice.18 But a court may not relax the 180-day period by more than 10 days.19 We have strictly enforced the time limit provided in Criminal Rule 35(b).20 Avery did not file his motion for relief under Criminal Rule 35(b), and even if he had, it is uneontested that this motion would have been untimely.
We conclude that Judge Kauvar has no authority to modify Avery’s sentence. We therefore vacate Judge Kauvar’s order setting a sentencing hearing to review Avery’s sentence.
We do not decide the issues that Avery did not raise either in the trial court or in his reply to the State’s petition
The parties raised an issue in this court that they did not present in the trial court. Avery contends that Almendárez-Torres, which allows a defendant’s prior convictions to be proven to the court without a jury finding, is questionable authority. He urges us to anticipate that the Supreme Court will conclude that Almendárez-Torres was incorrectly decided and will hold that the government must prove to a jury beyond a reasonable doubt any prior conviction that increases a defendant’s maximum sentence.
In a related argument, which he first raises in his opening brief, Avery argues that, under Alaska law, the four aggravating factors in this case were elements of his offense, and therefore, the State had to obtain an indictment from a grand jury and prove these aggravating factors to a jury beyond a reasonable doubt. These issues were never presented to the trial court or raised in the petition for review that this court granted. We accordingly decline to address these issues.
The order setting a resentencing hearing is REVERSED.
COATS, Chief Judge, concurs.
. 542 U.S. 296, 124 S.Ct. 2531, 159 L.Ed.2d 403 (2004).
. United States v. Booker, 543 U.S. 220, 244, 125 S.Ct. 738, 756, 160 L.Ed.2d 621 (2005).
.523 U.S. 224, 118 S.Ct. 1219, 140 L.Ed.2d 350 (1998).
. AS 11.71.040(a).
. AS 12.55.125(e)(3).
. Avery v. State, Alaska App. Memorandum Opinion and Judgment No. 4906 (Aug. 11, 2004), 2004 WL 1782553.
. Booker, 543 U.S. at 244, 125 S.Ct. at 756.
. 118 P.3d 11, 15 (Alaska App.2005).
. Id. at 15.
. Id.; Grohs v. State, 118 P.3d 1080, 1083 (Alaska App.2005); Edmonds v. State, 118 P.3d 17, 20 (Alaska App.2005).
. AS 12.55.155(c)(7).
12. Milligrock, 118 P.3d at 16.
. Id.
. Id.
. 118 P.3d 1080 (Alaska App.2005).
. Id. at 1083-84.
. Id. at 1084 (citation omitted).
. See Alaska Crim. R. 53; Thomas v. State, 566 P.2d 630, 638-39 (Alaska 1977).
. Alaska Crim. R. 35(g).
. See, e.g., State v. Couch, 991 P.2d 1286, 1287-88 (Alaska App.1999); State v. Tinsley, 928 P.2d 1220, 1223 (Alaska App.1996).