C#中关于对象的时间字段、时区设置

神之眼

1 天前

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假设有实体类Person

public class Person : object
{
    public string? Name;
    public DateTimeOffset Born;
    
    public override string ToString()
    {
        return $"{Name} was born on {Born:d}.";
    }
}

public class Person : object
{
    public string? Name;
    public DateTimeOffset Born;
    
    public override string ToString()
    {
        return $"{Name} was born on {Born:d}.";
    }
}

Swift

测试实例化对象

Person p = new()
{
    Name = "Jerry",
    Born = new DateTimeOffset(
    year: 1965, month: 12, day: 22,
    hour: 16, minute: 28, second: 0,
    offset: TimeSpan.FromHours(-5)) // US Eastern Standard Time.
};

WriteLine(p);

Person p = new()
{
    Name = "Jerry",
    Born = new DateTimeOffset(
    year: 1965, month: 12, day: 22,
    hour: 16, minute: 28, second: 0,
    offset: TimeSpan.FromHours(-5)) // US Eastern Standard Time.
};

WriteLine(p);

Swift

Jerry was born on 22/12/1965.

Jerry was born on 22/12/1965.

Swift

**关于new DateTimeOffset（）初始化参数offset 的含义**：

该参数表示该时间点相对于协调世界时（UTC）的时差

TimeSpan.FromHours(-5) 表示该时间属于 UTC-5 时区（如北美东部标准时间 EST）。
示例中的时间 1965-12-22 16:28:00 实际等同于：
UTC 时间 1965-12-22 21:28:00（因为 16:28 + 5小时 = 21:28 UTC）。

若要表达中国时间，中国采用 UTC+8 时区（无夏令时），设置方式如下：

bob.Born = new DateTimeOffset(
  year: 1965, month: 12, day: 22,
  hour: 16, minute: 28, second: 0,
  offset: TimeSpan.FromHours(8) // UTC+8（北京时间）
);

bob.Born = new DateTimeOffset(
  year: 1965, month: 12, day: 22,
  hour: 16, minute: 28, second: 0,
  offset: TimeSpan.FromHours(8) // UTC+8（北京时间）
);

Swift

替代方案（推荐）：

使用 .ToOffset() 方法转换时区更安全

// 先定义 UTC 时间或本地时间
var utcTime = new DateTime(1965, 12, 22, 8, 28, 0, DateTimeKind.Utc);
p.Born = new DateTimeOffset(utcTime).ToOffset(TimeSpan.FromHours(8));

// 先定义 UTC 时间或本地时间
var utcTime = new DateTime(1965, 12, 22, 8, 28, 0, DateTimeKind.Utc);
p.Born = new DateTimeOffset(utcTime).ToOffset(TimeSpan.FromHours(8));

Swift

注意⚠️

对夏令时区域，建议用 TimeZoneInfo 转换（如 TimeZoneInfo.ConvertTimeBySystemTimeZoneId）。

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