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Calculating the day of week from a date

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This commit is contained in:
Rhys Weatherley 2012-06-11 10:05:24 +10:00
parent 00eea28357
commit fa7df64f52
4 changed files with 64 additions and 0 deletions
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41
libraries/RTC/RTC.cpp
View File

@ -66,6 +66,21 @@ static uint8_t monthLengths[] = {
31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};
static unsigned int monthOffsets[] = {
0,
31,
31 + 28,
31 + 28 + 31,
31 + 28 + 31 + 30,
31 + 28 + 31 + 30 + 31,
31 + 28 + 31 + 30 + 31 + 30,
31 + 28 + 31 + 30 + 31 + 30 + 31,
31 + 28 + 31 + 30 + 31 + 30 + 31 + 31,
31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30,
31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31,
31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30
};
inline bool isLeapYear(unsigned int year)
{
if ((year % 100) == 0)
@ -368,6 +383,32 @@ void RTC::adjustYears(RTCDate *date, uint8_t flags)
date->day = len;
}
/**
* \enum RTC::DayOfWeek
* \brief Day of the week corresponding to a date.
*
* \sa dayOfWeek()
*/
/**
* \brief Returns the day of the week corresponding to \a date.
*
* This function is only guaranteed to produce meaningful values
* for years between 2000 and 2099.
*/
RTC::DayOfWeek RTC::dayOfWeek(const RTCDate *date)
{
// The +4 here adjusts for Jan 1, 2000 being a Saturday.
unsigned long daynum = date->day + 4;
daynum += monthOffsets[date->month - 1];
if (date->month > 2 && isLeapYear(date->year))
++daynum;
daynum += 365UL * (date->year - 2000);
if (date->year > 2000)
daynum += ((date->year - 2001) / 4) + 1;
return (DayOfWeek)((daynum % 7) + 1);
}
/**
* \class RTCTime RTC.h <RTC.h>
* \brief Stores time information from a realtime clock chip.

13
libraries/RTC/RTC.h
View File

@ -52,6 +52,17 @@ public:
RTC();
~RTC();
enum DayOfWeek
{
Monday = 1,
Tuesday,
Wednesday,
Thursday,
Friday,
Saturday,
Sunday,
};
virtual bool hasUpdates();
virtual void readTime(RTCTime *value);
@ -82,6 +93,8 @@ public:
static void adjustMonths(RTCDate *date, uint8_t flags);
static void adjustYears(RTCDate *date, uint8_t flags);
static DayOfWeek dayOfWeek(const RTCDate *date);
private:
unsigned long midnight;
RTCDate date;

5
libraries/RTC/examples/DumpRTC/DumpRTC.pde
View File

@ -11,6 +11,10 @@ This example is placed into the public domain.
SoftI2C i2c(A4, A5);
DS3232RTC rtc(i2c);
const char *days[] = {
"Mon, ", "Tue, ", "Wed, ", "Thu, ", "Fri, ", "Sat, ", "Sun, "
};
const char *months[] = {
" Jan ", " Feb ", " Mar ", " Apr ", " May ", " Jun ",
" Jul ", " Aug ", " Sep ", " Oct ", " Nov ", " Dec "
@ -52,6 +56,7 @@ void loop() {
Serial.println();
Serial.print("Date: ");
Serial.print(days[RTC::dayOfWeek(&date) - 1]);
Serial.print(date.day, DEC);
Serial.print(months[date.month - 1]);
Serial.print(date.year);

5
libraries/RTC/examples/TestRTC/TestRTC.pde
View File

@ -38,6 +38,10 @@ DS3232RTC rtc(i2c);
char buffer[64];
size_t buflen;
const char *days[] = {
"Mon, ", "Tue, ", "Wed, ", "Thu, ", "Fri, ", "Sat, ", "Sun, "
};
const char *months[] = {
" Jan ", " Feb ", " Mar ", " Apr ", " May ", " Jun ",
" Jul ", " Aug ", " Sep ", " Oct ", " Nov ", " Dec "
@ -192,6 +196,7 @@ void cmdDate(const char *args)
// Read the current date.
rtc.readDate(&date);
Serial.print(days[RTC::dayOfWeek(&date) - 1]);
Serial.print(date.day, DEC);
Serial.print(months[date.month - 1]);
Serial.println(date.year, DEC);