火狐浏览器
navigator.userAgent
"Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:71.0) Gecko/20100101 Firefox/71.0"
Date.parse('9999/12/31 00:00:00.000')
NaN
Date.parse('9999-12-31 00:00:00.000')
253402185600000
Date.parse('9999/12/31T00:00:00')
NaN
Date.parse('9999-12-31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00.000')
NaN
Date.parse('9999-12-31 00:00:00.000')
253402185600000
Date.parse('9999-12-31T00:00:00')
253402185600000
谷歌浏览器
navigator.userAgent
"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
Date.parse('9999/12/31 00:00:00.000')
253402185600000
Date.parse('9999-12-31 00:00:00.000')
253402185600000
Date.parse('9999/12/31T00:00:00')
NaN
Date.parse('9999-12-31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00.000')
253402185600000
Date.parse('9999-12-31 00:00:00.000')
253402185600000
Date.parse('9999-12-31T00:00:00')
253402185600000
UC浏览器
navigator.userAgent
"Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 UBrowser/6.2.3964.2 Safari/537.36"
Date.parse('9999/12/31 00:00:00.000')
253402185600000
Date.parse('9999-12-31 00:00:00.000')
253402185600000
Date.parse('9999/12/31T00:00:00')
NaN
Date.parse('9999-12-31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00.000')
253402185600000
Date.parse('9999-12-31 00:00:00.000')
253402185600000
Date.parse('9999-12-31T00:00:00')
253402214400000 //错误结果,多了8小时
360极速浏览器(极速模式)
navigator.userAgent
"Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36"
Date.parse('9999/12/31 00:00:00.000')
253402185600000
Date.parse('9999-12-31 00:00:00.000')
253402185600000
Date.parse('9999/12/31T00:00:00')
NaN
Date.parse('9999-12-31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00.000')
253402185600000
Date.parse('9999-12-31 00:00:00.000')
253402185600000
Date.parse('9999-12-31T00:00:00')
253402185600000
360浏览器(兼容模式)
navigator.userAgent
"Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; .NET CLR 2.0.50727; .NET CLR 3.0.30729; .NET CLR 3.5.30729; rv:11.0) like Gecko"
Date.parse('9999/12/31 00:00:00.000')
NaN
Date.parse('9999-12-31 00:00:00.000')
NaN
Date.parse('9999/12/31T00:00:00')
25340218920000 //错误结果
Date.parse('9999-12-31 00:00:00')
NaN
Date.parse('9999/12/31 00:00:00')
253402185600000
Date.parse('9999/12/31 00:00:00.000')
NaN
Date.parse('9999-12-31 00:00:00.000')
NaN
Date.parse('9999-12-31T00:00:00')
253402185600000
综上所述:兼容大部分浏览器的格式是Date.parse('9999-12-31 00:00:00.000')