1、算法
时间是有周期规律的，4年一个周期（平年、平年、平年、闰年）共计1461天。Windows上C库函数time(NULL)返回的是从1970年1月1日以来的毫秒数，我们最后算出来的年数一定要加上这个基数1970。总的天数除以1461就可以知道经历了多少个周期；总的天数对1461取余数就可以知道剩余的不足一个周期的天数，对这个余数进行判断也就可以得到月份和日了。
当然了，C语言库函数：localtime就可以获得一个时间戳对应的具体日期了，这里 主要说的是实现的一种算法。
2、C语言代码实现
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
|
int nTime = time(NULL);//得到当前系统时间int nDays = nTime/DAYMS + 1;//time函数获取的是从1970年以来的毫秒数，因此需要先得到天数int nYear4 = nDays/FOURYEARS;//得到从1970年以来的周期（4年）的次数int nRemain = nDays%FOURYEARS;//得到不足一个周期的天数int nDesYear = 1970 + nYear4*4;int nDesMonth = 0, nDesDay = 0;bool bLeapYear = false;if ( nRemain<365 )//一个周期内，第一年{//平年}else if ( nRemain<(365+365) )//一个周期内，第二年{//平年nDesYear += 1;nRemain -= 365;}else if ( nRemain<(365+365+365) )//一个周期内，第三年{//平年nDesYear += 2;nRemain -= (365+365);}else//一个周期内，第四年，这一年是闰年{//润年nDesYear += 3;nRemain -= (365+365+365);bLeapYear = true;}GetMonthAndDay(nRemain, nDesMonth, nDesDay, bLeapYear); |
计算月份和日期的函数：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
|
static const int MON1[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; //平年static const int MON2[12] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; //闰年static const int FOURYEARS = (366 + 365 +365 +365); //每个四年的总天数static const int DAYMS = 24*3600; //每天的毫秒数void GetMonthAndDay(int nDays, int& nMonth, int& nDay, bool IsLeapYear){ int *pMonths = IsLeapYear?MON2:MON1; //循环减去12个月中每个月的天数，直到剩余天数小于等于0，就找到了对应的月份 for ( int i=0; i<12; ++i ) { int nTemp = nDays - pMonths[i]; if ( nTemp<=0 ) { nMonth = i+1; if ( nTemp == 0 )//表示刚好是这个月的最后一天，那么天数就是这个月的总天数了 nDay = pMonths[i]; else nDay = nDays; break; } nDays = nTemp; }} |
3、附上C语言库函数的实现
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
<pre name="code" class="cpp">/****errno_t _gmtime32_s(ptm, timp) - convert *timp to a structure (UTC)**Purpose:* Converts the calendar time value, in 32 bit internal format, to* broken-down time (tm structure) with the corresponding UTC time.**Entry:* const time_t *timp - pointer to time_t value to convert**Exit:* errno_t = 0 success* tm members filled-in* errno_t = non zero* tm members initialized to -1 if ptm != NULL**Exceptions:********************************************************************************/errno_t __cdecl _gmtime32_s (struct tm *ptm,const __time32_t *timp){__time32_t caltim;/* = *timp; *//* calendar time to convert */int islpyr = 0; /* is-current-year-a-leap-year flag */REG1 int tmptim;REG3 int *mdays;/* pointer to days or lpdays */struct tm *ptb = ptm;_VALIDATE_RETURN_ERRCODE( ( ptm != NULL ), EINVAL )memset( ptm, 0xff, sizeof( struct tm ) );_VALIDATE_RETURN_ERRCODE( ( timp != NULL ), EINVAL )caltim = *timp;_VALIDATE_RETURN_ERRCODE_NOEXC( ( caltim >= _MIN_LOCAL_TIME ), EINVAL )/* * Determine years since 1970. First, identify the four-year interval * since this makes handling leap-years easy (note that 2000 IS a * leap year and 2100 is out-of-range). */tmptim = (int)(caltim / _FOUR_YEAR_SEC);caltim -= ((__time32_t)tmptim * _FOUR_YEAR_SEC);/* * Determine which year of the interval */tmptim = (tmptim * 4) + 70; /* 1970, 1974, 1978,...,etc. */if ( caltim >= _YEAR_SEC ) { tmptim++; /* 1971, 1975, 1979,...,etc. */ caltim -= _YEAR_SEC; if ( caltim >= _YEAR_SEC ) {tmptim++; /* 1972, 1976, 1980,...,etc. */caltim -= _YEAR_SEC;/* * Note, it takes 366 days-worth of seconds to get past a leap * year. */if ( caltim >= (_YEAR_SEC + _DAY_SEC) ) {tmptim++; /* 1973, 1977, 1981,...,etc. */caltim -= (_YEAR_SEC + _DAY_SEC);}else {/* * In a leap year after all, set the flag. */islpyr++;} }}/* * tmptim now holds the value for tm_year. caltim now holds the * number of elapsed seconds since the beginning of that year. */ptb->tm_year = tmptim;/* * Determine days since January 1 (0 - 365). This is the tm_yday value. * Leave caltim with number of elapsed seconds in that day. */ptb->tm_yday = (int)(caltim / _DAY_SEC);caltim -= (__time32_t)(ptb->tm_yday) * _DAY_SEC;/* * Determine months since January (0 - 11) and day of month (1 - 31) */if ( islpyr ) mdays = _lpdays;else mdays = _days;for ( tmptim = 1 ; mdays[tmptim] < ptb->tm_yday ; tmptim++ ) ;ptb->tm_mon = --tmptim;ptb->tm_mday = ptb->tm_yday - mdays[tmptim];/* * Determine days since Sunday (0 - 6) */ptb->tm_wday = ((int)(*timp / _DAY_SEC) + _BASE_DOW) % 7;/* * Determine hours since midnight (0 - 23), minutes after the hour * (0 - 59), and seconds after the minute (0 - 59). */ptb->tm_hour = (int)(caltim / 3600);caltim -= (__time32_t)ptb->tm_hour * 3600L;ptb->tm_min = (int)(caltim / 60);ptb->tm_sec = (int)(caltim - (ptb->tm_min) * 60);ptb->tm_isdst = 0;return 0;} |
以上这篇C语言实现时间戳转日期的算法(推荐)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持服务器之家。
