It's not normal, but it is allowed, despite what most people think. One year is the maximum possible period of initial admission. 8 CFR 214.2(b)(1):
(b) Visitors -
(1) General. Any B-1 visitor for business or B-2 visitor for pleasure may be admitted for not more than one year and may be granted extensions of temporary stay in increments of not more than six months each, except that alien members of a religious denomination coming temporarily and solely to do missionary work in behalf of a religious denomination may be granted extensions of not more than one year each, provided that such work does not involve the selling of articles or the solicitation or acceptance of donations. Those B-1 and B-2 visitors admitted pursuant to the waiver provided at § 212.1(e) of this chapter may be admitted to and stay on Guam for period not to exceed fifteen days and are not eligible for extensions of stay.
Since your passport and the online I-94 database agree that you were admitted until 2 April 2020, you may remain in the US until that day.
However, if you do something different from what you told the officer when you entered, you might be met with a charge of deception. I am not aware of this happening in the US, but it seems fairly common in the UK.
You could protect yourself against suspicion by leaving the US within the five months and then coming back, saying that you have changed your plans because of the extended period of admission. On the other hand, if you have firm evidence of your original plans, you might not need to do that.
Also be aware of tax considerations. If you remain in the US for over 183 days, you will become liable to report and figure income tax on your worldwide income.