swift日期

日历

1. Calendar.Component

属性	作用
era	BCE(BC、公元前) = 0; CE(AD、公元) = 1
quarter	季度
year	年
month	月
day	日
hour	时
minute	分
second	秒
nanosecond	纳秒
weekday	星期几
weekdayOrdinal	指定日期是本月的第几个星期数（如：2010/9/27是本月的第四个星期三）
weekOfMonth	指定日期是一个月中的第几周
weekOfYear	指定日期是一年中的第几周
yearForWeekOfYear	指定日期周编号年份，PS：ISO 8601定义了一个周编号年份，由52周或53周（364天或371天）组成，这样一年的第一周被指定为包含一年中第一个星期四的一周。
calendar	日历单位的标识符
timeZone	时区（UTC +00:00 校准的全球时间、GMT 0:00 格林尼治标准时间）

2. 指定日期范围

extension Date {
    var rangeOfDay: Range {
        Calendar.current.range(of: .day, in: .month, for: self)!
    }
    
    func firstDay(in component: Calendar.Component) -> Date {
        var dateComponents = Calendar.current.dateComponents([.year, .month, .day, .hour, .minute, .second], from: self)
        
        switch component {
        case .year:
            dateComponents.month = 1
            fallthrough
        case .month:
            dateComponents.day = 1
            fallthrough
        case .day:
            dateComponents.hour = 0
            dateComponents.minute = 0
            dateComponents.second = 0
        default:
            break
        }
        return Calendar.current.date(from: dateComponents) ?? self
    }
    
    func endDay(in component: Calendar.Component) -> Date {
        var dateComponents = Calendar.current.dateComponents([.year, .month, .day, .hour, .minute, .second], from: self)
        
        switch component {
        case .year:
            dateComponents.month = 12
            fallthrough
        case .month:
            dateComponents.day = rangeOfDay.max() ?? 0
            fallthrough
        case .day:
            dateComponents.hour = 23
            dateComponents.minute = 59
            dateComponents.second = 59
        default:
            break
        }
        return Calendar.current.date(from: dateComponents) ?? self
    }
}
let range = Date().rangeOfDay
/// 1..<31
let firstDate = Date().firstDay(in: .year)
/// 2018-12-31 16:00:00 +0000(2019-01-01 00:00:00 +8000)
let endDate = Date().endDay(in: .year)
/// 2019-12-30 15:59:59 +0000(2019-12-30 23:59:59 +80000)

时区

1. 获取已知时区

TimeZone.knownTimeZoneIdentifiers

2. 当前时区名称和缩写

let zone = TimeZone.current
/// 名称
zone.identifier
/// 缩写
zone.abbreviation()
/// 当前时区与零时区的间隔秒数
zone.secondsFromGMT()

字符串转换成时间

/// 北京时间东八区，比美国快了13小时
let timeStr = "2018-12-12 10:48:46 GTM +8:00"
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss ZZZZ"
let date = formatter.date(from: timeStr)

/// 24小时制
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
formatter.string(from: date!)

/// 中国：年月日 上下午 时间
formatter.locale = Locale(identifier: "zh_CN")
formatter.dateStyle = .medium
formatter.timeStyle = .medium
formatter.string(from: date!)

dateFormat	项目
a	AM/PM (上午/下午)
A	0~86399999 (一天的第A微秒)
ccc	Sun/Mon/Tue/Wed/Thu/Fri/Sat (星期几简写)
cccc	Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday (星期几全拼)
d	1~31 (月份的第几天, 带0)
D	1~366 (年份的第几天,带0)
e	1~7 (一周的第几天, 带0)
E~EEE	Sun/Mon/Tue/Wed/Thu/Fri/Sat (星期几简写)
EEEE	Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday (星期几全拼)
F	1~5 (每月的第几周, 一周的第一天为周一)
g	Julian Day Number (number of days since 4713 BC January 1) 未知
G~GGG	BC/AD (Era Designator Abbreviated) 未知
GGGG	Before Christ/Anno Domini 未知
h	1~12 (0 padded Hour (12hr)) 带0的时, 12小时制
H	0~23 (0 padded Hour (24hr)) 带0的时, 24小时制
k	1~24 (0 padded Hour (24hr) 带0的时, 24小时制
K	0~11 (0 padded Hour (12hr)) 带0的时, 12小时制
L/LL	1~12 (0 padded Month) 第几月
LLL	Jan/Feb/Mar/Apr/May/Jun/Jul/Aug/Sep/Oct/Nov/Dec 月份简写
LLLL	January/February/March/April/May/June/July/August/September/October/November/December 月份全称
m	0~59 (0 padded Minute) 分钟
M/MM	1~12 (0 padded Month) 第几月
MMM	Jan/Feb/Mar/Apr/May/Jun/Jul/Aug/Sep/Oct/Nov/Dec
MMMM	January/February/March/April/May/June/July/August/September/October/November/December
q/qq	1~4 (0 padded Quarter) 第几季度
qqq	Q1/Q2/Q3/Q4 季度简写
qqqq	1st quarter/2nd quarter/3rd quarter/4th quarter 季度全拼
Q/QQ	1~4 (0 padded Quarter) 同小写
QQQ	Q1/Q2/Q3/Q4 同小写
QQQQ	1st quarter/2nd quarter/3rd quarter/4th quarter 同小写
s	0~59 (0 padded Second) 秒数
S	(rounded Sub-Second) 未知
u	(0 padded Year) 未知
v~vvv	(General GMT Timezone Abbreviation) 常规GMT时区的编写
vvvv	(General GMT Timezone Name) 常规GMT时区的名称
w	1~53 (0 padded Week of Year, 1st day of week = Sunday, NB: 1st week of year starts from the last Sunday of last year) 一年的第几周, 一周的开始为周日,第一周从去年的最后一个周日起算
W	1~5 (0 padded Week of Month, 1st day of week = Sunday) 一个月的第几周
y/yyyy	(Full Year) 完整的年份
yy/yyy	(2 Digits Year) 2个数字的年份
Y/YYYY	(Full Year, starting from the Sunday of the 1st week of year) 这个年份未知干嘛用的
YY/YYY	(2 Digits Year, starting from the Sunday of the 1st week of year) 这个年份未知干嘛用的
z~zzz	(Specific GMT Timezone Abbreviation) 指定GMT时区的编写
zzzz	(Specific GMT Timezone Name) Z: +0000 (RFC 822 Timezone) 指定GMT时区的名称

DateComponents转化为时间

extension Date {
    init?(components: DateComponents) {
        guard let date = Calendar.current.date(from: components) else {
            return nil
        }
        self = date
    }

    static func + (lhs: inout Date, rhs: DateComponents) -> Date? {
        return Calendar.current.date(byAdding: rhs, to: lhs)
    }

    static func - (lhs: inout Date, rhs: DateComponents) -> Date? {
        var right = rhs

        right.era = rhs.era != nil ? -rhs.era! : nil

        right.year = rhs.year != nil ? -rhs.year! : nil
        right.month = rhs.month != nil ? -rhs.month! : nil
        right.day = rhs.day != nil ? -rhs.day! : nil

        right.hour = rhs.hour != nil ? -rhs.hour! : nil
        right.minute = rhs.minute != nil ? -rhs.minute! : nil
        right.second = rhs.second != nil ? -rhs.second! : nil
        right.nanosecond = rhs.nanosecond != nil ? -rhs.nanosecond! : nil

        return Calendar.current.date(byAdding: right, to: lhs)
    }
}

let components = DateComponents(year: 2001, month: 5, day: 10)
let date = Date(components: components)
/// Optional(2001-05-09 16:00:00 +0000)
let add = DateComponents(month: 5, day: 5)
let resultDate = date! + add
/// Optional(2001-10-14 16:00:00 +0000)
let resultDate1 = date - add
/// Optional(2000-12-04 16:00:00 +0000)

时间组件化

extension Date {
    func value(for component: Calendar.Component) -> Int {
        var dateComponents = Calendar.current.dateComponents([component], from: self)
      
        switch component {
        case .quarter:
            let month = value(for: .month)
            
            if month < 4 {
                dateComponents.quarter = 1
            } else if month < 7 {
                dateComponents.quarter = 2
            } else if month <= 10 {
                dateComponents.quarter = 3
            } else {
                dateComponents.quarter = 4
            }
        case .calendar, .timeZone:
            
            if dateComponents.calendar == nil {
                dateComponents.calendar = Calendar.current
            }
        default:
            break
        }
        return dateComponents.value(for: component) ?? 0
    }
}

let date0 = Date().value(for: .year)
/// 2019