var culture = CultureInfo.CreateSpecificCulture("zh-CN");
var dateformat = new DateTimeFormatInfo
{
    ShortDatePattern = "yyyy-MM-dd",
    LongDatePattern = "yyyy-MM-dd hh:mm:ss"
};
culture.DateTimeFormat = dateformat;

var supportedCultures = new[]
{
    culture
};

app.UseRequestLocalization(new RequestLocalizationOptions
{
    DefaultRequestCulture = new RequestCulture(culture),
    SupportedCultures = supportedCultures,
    SupportedUICultures = supportedCultures
});

From:
https://stackoverflow.com/questions/56748968/how-to-set-date-formats-and-culture-in-asp-net-core-razor-pages-2-2