documentclass[12pt,reqno,a4paper]{amsart}
%usepackage[utf8]{inputenc} % not needed with up-to-date TeX systems
usepackage[english]{babel}

usepackage{amsmath,amsthm,amsfonts,amssymb}
usepackage{mathtools}
usepackage{color}

usepackage{mathrsfs}
usepackage[all]{xy}
usepackage{tikz-cd}
usepackage[normalem]{ulem} % do you *really* need it?
usepackage{datetime}

usepackage{hyperref}

theoremstyle{definition}

newtheorem{theorem}{Theorem}[section]
newtheorem{construction}{Construction}
[section]
newtheorem{observation}{Observation}
newtheorem{corollary}{Corollary}[section]
newtheorem{lemma}{Lemma}[section]
newtheorem{definition}{Definition}[section]
newtheorem{remark}{Remark}[section]
newtheorem{proposition}{Proposition}[subsection]
renewcommand{qedsymbol}{$blacksquare$}
newtheorem{example}{Example}
newtheorem*{question}{Question}
newtheorem*{solution}{Solution}
newtheorem{exercise}{Exercise}

newcommand{mc}{mathcal}
newcommand{mf}{mathfrak}
newcommand{mb}{mathbb}
newcommand{xra}{xrightarrow}
newcommand{ra}{rightarrow}
newcommand{rra}{rightrightarrows}
pagestyle{myheadings}

textheight 9.3in
textwidth 6.5in
calclayout

% metadata

%date{today}


title{something}
author{someone}
address{somewhere}


begin{document}
    %today
begin{abstract}

end{abstract}
maketitle

end{document}