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
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
|
#include "common.h"
#include "time_convert.h"
void ConvertToAbsolute (const SYSTEMTIME * pstLoc, const SYSTEMTIME * pstDst, SYSTEMTIME * pstDstAbs)
{
static int iDays [12] = { 31, 28, 31, 30, 31, 30,
31, 31, 30, 31, 30, 31 } ;
int iDay ;
// Set up the aboluste date structure except for wDay, which we must find
pstDstAbs->wYear = pstLoc->wYear ; // Notice from local date/time
pstDstAbs->wMonth = pstDst->wMonth ;
pstDstAbs->wDayOfWeek = pstDst->wDayOfWeek ;
pstDstAbs->wHour = pstDst->wHour ;
pstDstAbs->wMinute = pstDst->wMinute ;
pstDstAbs->wSecond = pstDst->wSecond ;
pstDstAbs->wMilliseconds = pstDst->wMilliseconds ;
// Fix the iDays array for leap years
if ((pstLoc->wYear % 4 == 0) && ((pstLoc->wYear % 100 != 0) ||
(pstLoc->wYear % 400 == 0)))
{
iDays[1] = 29 ;
}
// Find a day of the month that falls on the same
// day of the week as the transition.
// Suppose today is the 20th of the month (pstLoc->wDay = 20)
// Suppose today is a Wednesday (pstLoc->wDayOfWeek = 3)
// Suppose the transition occurs on a Friday (pstDst->wDayOfWeek = 5)
// Then iDay = 31, meaning that the 31st falls on a Friday
// (The 7 is this formula avoids negatives.)
iDay = pstLoc->wDay + pstDst->wDayOfWeek + 7 - pstLoc->wDayOfWeek ;
// Now shrink iDay to a value between 1 and 7.
iDay = (iDay - 1) % 7 + 1 ;
// Now iDay is a day of the month ranging from 1 to 7.
// Recall that the wDay field of the structure can range
// from 1 to 5, 1 meaning "first", 2 meaning "second",
// and 5 meaning "last".
// So, increase iDay so it's the proper day of the month.
iDay += 7 * (pstDst->wDay - 1) ;
// Could be that iDay overshot the end of the month, so
// fix it up using the number of days in each month
if (iDay > iDays[pstDst->wMonth - 1])
iDay -= 7 ;
// Assign that day to the structure.
pstDstAbs->wDay = iDay ;
}
BOOL LocalGreaterThanTransition (const SYSTEMTIME * pstLoc, const SYSTEMTIME * pstTran)
{
FILETIME ftLoc, ftTran ;
LARGE_INTEGER liLoc, liTran ;
SYSTEMTIME stTranAbs ;
// Easy case: Just compare the two months
if (pstLoc->wMonth != pstTran->wMonth)
return (pstLoc->wMonth > pstTran->wMonth) ;
// Well, we're in a transition month. That requires a bit more work.
// Check if pstDst is in absolute or day-in-month format.
// (See documentation of TIME_ZONE_INFORMATION, StandardDate field.)
if (pstTran->wYear) // absolute format (haven't seen one yet!)
{
stTranAbs = * pstTran ;
}
else // day-in-month format
{
ConvertToAbsolute (pstLoc, pstTran, &stTranAbs) ;
}
// Now convert both date/time structures to large integers & compare
SystemTimeToFileTime (pstLoc, &ftLoc) ;
liLoc = * (LARGE_INTEGER *) (void *) &ftLoc ;
SystemTimeToFileTime (&stTranAbs, &ftTran) ;
liTran = * (LARGE_INTEGER *) (void *) &ftTran ;
return (liLoc.QuadPart > liTran.QuadPart) ;
}
BOOL MySystemTimeToTzSpecificLocalTime(const TIME_ZONE_INFORMATION *ptzi, const SYSTEMTIME *pstUtc, SYSTEMTIME *pstLoc) {
// st is UTC
FILETIME ft ;
LARGE_INTEGER li ;
SYSTEMTIME stDst ;
// If we're running under NT, just call the real function
if (!(0x80000000 & GetVersion()))
return SystemTimeToTzSpecificLocalTime ((TIME_ZONE_INFORMATION *) ptzi, (SYSTEMTIME *) pstUtc, pstLoc) ;
// Convert time to a LARGE_INTEGER and subtract the bias
SystemTimeToFileTime (pstUtc, &ft) ;
li = * (LARGE_INTEGER *) (void *) &ft;
li.QuadPart -= (LONGLONG) 600000000 * ptzi->Bias ;
// Convert to a local date/time before application of daylight saving time.
// The local date/time must be used to determine when the conversion occurs.
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime (&ft, pstLoc) ;
// Find the time assuming Daylight Saving Time
li.QuadPart -= (LONGLONG) 600000000 * ptzi->DaylightBias ;
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime (&ft, &stDst) ;
// Now put li back the way it was
li.QuadPart += (LONGLONG) 600000000 * ptzi->DaylightBias ;
if (ptzi->StandardDate.wMonth) // ie, daylight savings time
{
// Northern hemisphere
if ((ptzi->DaylightDate.wMonth < ptzi->StandardDate.wMonth) &&
(stDst.wMonth >= pstLoc->wMonth) && // avoid the end of year problem
LocalGreaterThanTransition (pstLoc, &ptzi->DaylightDate) &&
!LocalGreaterThanTransition (&stDst, &ptzi->StandardDate))
{
li.QuadPart -= (LONGLONG) 600000000 * ptzi->DaylightBias ;
}
// Southern hemisphere
else if ((ptzi->StandardDate.wMonth < ptzi->DaylightDate.wMonth) &&
(!LocalGreaterThanTransition (&stDst, &ptzi->StandardDate) ||
LocalGreaterThanTransition (pstLoc, &ptzi->DaylightDate)))
{
li.QuadPart -= (LONGLONG) 600000000 * ptzi->DaylightBias ;
}
else
{
li.QuadPart -= (LONGLONG) 600000000 * ptzi->StandardBias ;
}
}
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime (&ft, pstLoc) ;
return TRUE ;
}
VOID MyGetSystemTime(LPSYSTEMTIME lpSystemTime) {
//TIME_ZONE_INFORMATION tzi;
//FILETIME ft;
//LARGE_INTEGER li;
GetSystemTime(lpSystemTime);
//GetTimeZoneInformation(&tzi);
/*
// the following corrects for the condition that occurs when 'automatically adjust for daylight savings' is off, but
// local timezone info says it is daylight savings time...
// it assumes that the timezone has not been adjusted but the time has instead - resulting in wrong GMT in the system clock
if(tzi.StandardDate.wMonth != 0 && tzi.DaylightBias == 0 && tzi.StandardBias == 0) {
// Northern hemisphere
if ((tzi.DaylightDate.wMonth < tzi.StandardDate.wMonth) &&
LocalGreaterThanTransition (lpSystemTime, &tzi.DaylightDate) &&
!LocalGreaterThanTransition (lpSystemTime, &tzi.StandardDate))
{
// add one hour to the system time
SystemTimeToFileTime(lpSystemTime, &ft);
li = * (LARGE_INTEGER *) (void *) &ft;
li.QuadPart += (LONGLONG) 600000000 * 60;
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime(&ft, lpSystemTime);
}
// Southern hemisphere
else if ((tzi.StandardDate.wMonth < tzi.DaylightDate.wMonth) &&
(!LocalGreaterThanTransition (lpSystemTime, &tzi.StandardDate) ||
LocalGreaterThanTransition (lpSystemTime, &tzi.DaylightDate)))
{
// add one hour to the system time
SystemTimeToFileTime(lpSystemTime, &ft);
li = * (LARGE_INTEGER *) (void *) &ft;
li.QuadPart += (LONGLONG) 600000000 * 60;
ft = * (FILETIME *) (void *) &li ;
FileTimeToSystemTime(&ft, lpSystemTime);
}
}
*/
}
|
