Abby Lee Miller's surrender date for her federal prison sentence of one year and one day has been delayed, ET can confirm.

Miller was expected to turn herself in on June 30, but ET has exclusively learned the date has been postponed until July 12. At this time it is not known why the date was changed.

EXCLUSIVE: Everything Abby Lee Miller Told ET About Prison, From Calling It a 'Vacation' to How She Prepared

The Dance Moms star was sentenced on May 9, 2017, giving her just over two months to prepare before the official surrender. In addition to her prison time, Miller was also ordered by Chief Judge Joy Flowers Conti of Philadelphia, Pennsylvania, to pay a $40,000 fine and serve two years probation after her time behind bars.

ET has also learned that Miller recently filmed a special for Lifetime regarding her sentencing. The special is all about Miller and does not feature other cast members from the Dance Moms franchise.

A source close to Miller tells ET that the special was shot in Los Angeles and was conducted by a news journalist. The source described the interview as "riveting," adding that Miller "discussed everything" and was "very emotional" and "broke down a lot."

At her sentencing hearing, Miller sobbed as she made a plea for leniency to the judge. "My friends and colleagues have shed tears because of my careless mistakes. I have accepted responsibility for my actions and plead guilty to the two charges against me," she said. "I know that my future is uncertain. I can only assure you that I will never be in front of a court again."

"Somehow you got caught up in the fame and lost your moral compass," Conti told Miller at the time. "I hope when you get out the stars align for you."

EXCLUSIVE: Abby Lee Miller Attends Sentencing, Admits She’s ‘Nervous’ Ahead of Entering Courtroom

ET spoke with Miller immediately after her sentencing.

"I feel relieved," she told ET, along with other reporters, outside the courthouse. "I feel peaceful."

Part of that peace comes from knowing how she'll keep busy. Miller told ET exclusively that she's "pitching a new show."

"I have been so very successful - maybe that'll be some time to work," she continued. "There's dancing in it!"

WATCH: Abby Lee Miller's Tearful Exit in Sneak Peek From Her Final 'Dance Moms' Appearance

As positive as she sounded, Miller knew that adjusting to prison will take some time.

"There's a few physical limitations, dietary limitations [in prison], of course, but it'll be OK," she said, noting that she's not sure how working with the other women will be every day. "It's a realm of the world I know nothing about. I just know what I know and I do the best I can."

"I know that I didn't make the right decisions all the time," she added. "I think [the punishment's] just begun."

When asked what message she would like to tell her fans and supporters, she simply replied, "Live and learn."

WATCH: 'Dance Moms' Star Abby Lee Miller Plans to Pretend She's 'Shooting a Movie' While in Prison

Prior to the sentencing, Miller was singing a much different tune. In an exclusive sit-down interview with ET, Miller admitted that she wasn't ready to face prison. "No, no. No, no. I have to save my tears for the pillow," she said in March. "People ask me, 'Aren't you worried? Aren't you this, aren't you that?' I can't think about it. I have to live every day. In the end, I have to believe that everything will work out and the truth will come out. I think there's a lot more to it, there's a lot more moving parts to this case … like I teach my kids, life is not fair.”

EXCLUSIVE: Abby Lee Miller Breaks Down Before New Surgery: 'Nobody's Freaking Out If Something Happens to Me'

Prior to her court date, the 50-year-old dance instructor underwent gastric bypass surgery, a procedure that reduced her stomach by 80 percent. "I think this is the right time," Miller told ET in another exclusive interview in April. "People are saying, 'But your sentencing is coming up in a couple weeks!' And that is true, and I’m really nervous about that -- more than the surgery -- but there's no right time."

Additional reporting by Brendon Geoffrion and Darla Murray