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How to calculate amount of hours between two points in c#/Code review

Hello everyone I have a small programming problem which is probably a lot easier than i think. So I need to set the time to install Timespan opbject below to be 24 + time left to the next 4 pm. The below is C# pseudo code, it was written in notepad because at work I don't have an IDE, i also don't have much experience in programming using dates. i think my alghorithm will work but i guess there is a milion easier ways to do it. Please have a look:
//I need to make a timespan object which has 24 hours from current time + time left to the next 4pm
//The context is time to install, which user should see
Timespan TimeToInstall = new Timespan(23,59,59)
//Now I am taking the current time
Current = DateTime.Now
//Now I add the 24 hours to the current in order to create the next day date
Current.Add(TimeToInstall)
//Now creating the 4 PM on the next day
DateTime pm4 = new DateTime(Current.year,Current.month,Current.Day,16,0,0)
//Now checking if current is above or below 4 pm
if(Current.TimeOfDay < pm4){
TimeToInstall = TimeToInstall + (pm4 - Current)
}else if(Current.TimeOfDay > pm4){
pm4.AddDays(1)
TimeToInstall = TimeToInstall + (pm4 - Current)
}else {
//24 hours has passed and it is 4 pm so nothing to do here
}

TimeSpan can be negative. So just substract the TimeSpan for 4PM with current TimeOfDay, if you get negative value, add 24 hours.
var timeLeft = new TimeSpan(16, 0, 0) - DateTime.Now.TimeOfDay;
if (timeLeft.Ticks<0)
{
timeLeft = timeLeft.Add(new TimeSpan(24,0,0))
}

Based on your code:
DateTime now = DateTime.Now;
DateTime today4pmDateTime= new DateTime(now.Year, now.Month, now.Day, 16, 0, 0);
//Will hold the next 4pm DateTime.
DateTime next4pmDateTimeOccurrence = now.Hour >= 16 ? today4pmDateTime : today4pmDateTime.AddDays(1);
//From here you can do all the calculations you need
TimeSpan timeUntilNext4pm = next4pmDateTimeOccurrence - now;

The answer is really simple, I should have seened this earlier. The solution to these kind of problems is basically modular arithmetic. The client requirment was the popup to show 24+ time to next 4 pm (Don't ask i don't know) so if:
program runs at 13:00 then the clock should display 24 +3 = 27
when 16:00 it should be 24+24 which is 48
when 22:00 it shoould be 24 + 18 which is 42
Now I noticed that:
13 + 27 = 40
16 + 24 = 40
22 + 18 = 40
40 Modulo 24 = 16
So basically if I subtract the current time from 40 then I will be left with the difference:
40 - 13 = 27
40 - 16 = 24
40 - 22 = 18
So what I did is this:
TimeSpan TimeToInstall;
TimeSpan TimeGiven = new TimeSpan(23, 59, 59);
DateTime Now = DateTime.Now;
long TimeTo4 = (new TimeSpan(40, 0, 0).Ticks - Now.TimeOfDay.Ticks) + TimeGiven.Ticks;
TimeToInstall = TimeSpan.FromTicks(TimeTo4);
EDIT
The above was a trap
Corrected:
DateTime Now = DateTime.Now;
if (Now.Hour < 16)
{
long TimeTo4 = (new TimeSpan(40, 0, 0).Ticks - Now.TimeOfDay.Ticks);
TimeToInstall = TimeSpan.FromTicks(TimeTo4);
}
else
{
long TimeTo4 = (new TimeSpan(40, 0, 0).Ticks - Now.TimeOfDay.Ticks) + TimeGiven.Ticks;
TimeToInstall = TimeSpan.FromTicks(TimeTo4);
}

How to find the nearest date

I have the chart with three precisions.
Per hour,
Per 30 minutes,
Per 15 minutes.
Table with my data looks like this:
When i generating my chart i starting from the special date time for example from current date time
For example. When I starting from 18:00, and my preccision is per 15 minutes i need data from this times
18:00
17:45
17:30
17:15
17:00
...
In my data table I have data maximum per 3 minutes, so when i would like to get data from 17:15 my lambda query returns null because i have data only from 17:13 and 17:16.
So i need the query whitch return data nearest my data time. In upper example it's need to return data from 17:16.
I try DiffHours Method but it's don't work on MySQL. I need method working on MySQL and MSSQL
My current method looks like this:
var report = _reportRepository.FindBy(a => a.Fridge.FridgeIdentity == fridgeIdentity && a.CreatedDate.Year == fromTime.Year && a.CreatedDate.Month == fromTime.Month && a.CreatedDate.Day == fromTime.Day && a.CreatedDate.Hour == fromTime.Hour).FirstOrDefault();
but it's work only for per hour precision.
Thanks for help!

How about this, to get the closest time to a particular interval:
var fromTime = new DateTime(2016, 05, 20, 9, 0, 0);
var report = _reportRepository
.OrderBy(m =>m.CreatedDate > fromTime
? m.CreatedDate - fromTime
: fromTime - m.CreatedDate)
.Take(1);

You showed only limited code and weren't utterly specific about some points even after several questions about it, so I will assume the following:
you are able to create a working report for hourly precision, that means you are able to generate the list of desired times, e.g. 18:00, 18:15, 18:30 for a 15 minute interval (you just can't get the correct data for it) and these times are in the variable fromTime
you always have round times as report times, so e.g. 18:00, never 17:48
your closest entries can be both before and after the query time
if you do e.g. a 15 minutes report, and there is no value in your database with a datetime between 17:45:00 and 18:14:59, the report will not have any result for 18:00 (since your data covers every 3 minutes, it shouldn't be a problem anyway, except for pauses)
You have to use different queries for the 3 interval times. For 15 minutes use (assuming your table is called a):
select *
from
(select *,
convert(timestamp(date(date_add(CreatedDate, INTERVAL '7:30' MINUTE_SECOND)),
maketime(hour(date_add(CreatedDate, INTERVAL '7:30' MINUTE_SECOND)),
round(minute(date_add(CreatedDate, INTERVAL '7:30' MINUTE_SECOND)) div 15)
* 15, 0)), datetime) as filtertime
from a
) as withfilter
order by filtertime, abs(timediff(filtertime, CreatedDate)) ;
For the other intervals, you have to replace the interval accordingly (so replace 7:30 by half the interval time in minutes, and 15 by the interval time in minutes, so for 30 minute interval it would be:
select *
from
(select *,
convert(timestamp(date(date_add(CreatedDate, INTERVAL '15:00' MINUTE_SECOND)),
maketime(hour(date_add(CreatedDate, INTERVAL '15:00' MINUTE_SECOND)),
round(minute(date_add(CreatedDate, INTERVAL '15:00' MINUTE_SECOND)) div 30)
* 30, 0)), datetime) as filtertime
from a
) as withfilter
order by filtertime, abs(timediff(filtertime, CreatedDate)) ;
(and 30:00 and 60 for the hourly interval).
This will basically round your CreatedDate to the closest whole 15/30/60 minutes and order it by the timedifference to that. It will always round up, so a CreatedDate 2016-05-20 09:15:00 will be rounded to 2016-05-20 09:30:00 for a 30 minute interval, not to 2016-05-20 09:00:00.
You might want to take a direct look at the result to understand the final view; for your example data, e.g. 2016-05-20 09:18:40, it will first calculate the filtertimes 2016-05-20 09:15:00, 2016-05-20 09:30:00 and 2016-05-20 09:00:00 for the 3 queries 15 minutes, 30 minutes and 1 hour. It will then order it according to their distance to these times (3:40min, 11:20min and 18:40min).
Your reportfilter will have to use the filtertime instead of the CreatedDate time, and you have to add the minutes to compare to fromtime:
var report = _reportRepository.FindBy(a => a.Fridge.FridgeIdentity == fridgeIdentity
&& a.filtertime.Year == fromTime.Year
&& a.filtertime.Month == fromTime.Month
&& a.filtertime.Day == fromTime.Day
&& a.filtertime.Hour == fromTime.Hour
&& a.filtertime.Minute == fromTime.Minute).FirstOrDefault();

Errornous calculation of year/month/day between two dates

What I try to do is calculate the number of years, months and days between two dates.
Unfortunately, there is no method of the .NET Framework which can do this.
What I did is basically the following:
http://www.codeproject.com/Articles/28837/Calculating-Duration-Between-Two-Dates-in-Years-Mo
with a few adaptations from the comments of said website:
var monthDay = new[] { 31, 31, -1, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
DayCalculation:
if (fromDate.Day > toDate.Day)
{
increment = monthDay[toDate.Month - 1];
}
if (increment == -1)
{
increment = DateTime.IsLeapYear(toDate.Year) ? 29 : 28;
}
So I have the following effect:
Date1: 1979-01-30
Date2: 2013-03-01
And the output is: 34 Years, 1 Month, -1 Day
The expected output is: 34 Years, 1 Month, 1 Day
This effect happens every time, the Date2 is a date in march.
Do you know what is wrong with this calculation?
Or do you know a better solution how to achieve the desired result?
Thanks in advance
PS: I know that you can calculate the amount of days between two dates, but what I need is the amount of finished years, the amount of finished months, and the amount of finished days

Unfortunately, there is no method of the .NET Framework which can do this.
True, but there is Noda Time instead :) (It's my port of Joda Time to .NET, although there are quite a few differences between the two projects.)
LocalDate start = new LocalDate(1979, 1, 30);
LocalDate end = new LocalDate(2013, 3, 1);
Period period = Period.Between(start, end);
Console.WriteLine("{0} years, {1} months, {2} days",
period.Years, period.Months, period.Days);
Output:
34 years, 1 months, 1 days

Here is a way to calculate the difference without using an external library. Two dates are required. I assume that the first date is no later than the second date. Otherwise you will have to swap them for the calculation to be correct.
var first = new DateTime(1979, 1, 30);
var second = new DateTime(2013, 3, 1);
Here is how to compute the difference. You do not need a table to get the number of days in the month. That information is provided by the DateTime.DaysInMonth function.
var years = second.Year - first.Year;
var months = second.Month - first.Month;
if (months < 0) {
months += 12;
years -= 1;
}
var days = second.Day - first.Day;
if (days < 0) {
var daysInFirstMonth = DateTime.DaysInMonth(first.Year, first.Month);
days += daysInFirstMonth;
months -= 1;
}
Printing the computed values
Console.WriteLine("{0} year(s), {1} month(s), {2} day(s)", years, months, days);
will result in
34 year(s), 1 month(s), 2 day(s)
This produces the same results as the code that you have linked to. However, you expect to get 1 day instead of 2 days. I guess it depends on how you define "days between". If you prefer to count only January 31 as the day between you can subtract 1 from days. Then there will be 0 days between two adjacent days and -1 days "between the same date".

How to convert year, month and day to ticks without using DateTime

long ticks = new DateTime(2012, 1, 31).ToLocalTime().Ticks; // 634635684000000000
But how to do this without DateTime constructor ?
edit
What I actually want is to keep only the years, months and days from the ticks.
long ALL_Ticks = DateTime.Now.Ticks; // 634636033446495283
long Only_YearMonthDay = 634635684000000000; // how to do this ?
I want to use this in a linq-sql query using Linq.Translations.

If you only want the ticks for the date portion of the current datetime you could use:
long Only_YearMonthDay = DateTime.Now.Date.Ticks; //634635648000000000
//DateTime.Now.Date.Ticks + DateTime.Now.TimeOfDay.Ticks == DateTime.Now.Ticks

You could find out how many days are in the calculation and then multiply by 864,000,000,000 (which is how many ticks are in a day). Is that what you are looking for? Bit of documentation here : http://msdn.microsoft.com/en-us/library/system.timespan.ticksperday.aspx.
Happy coding,
Cheers,
Chris.
OK - didn't think this through properly! Ticks represent the amount of 100 nanosecond intervals since 12:00:00 midnight, January 1, 0001. You would need to calculate how many days have passed since that date and then multiply it by the ticks per day value!
If I understand you right, you are not worried about the ticks up to a particular time of the day?! So, it would be something along the lines of :
var ticksToDate = (DateTime.UtcNow - DateTime.MinValue).Days * 864000000000;
Does that answer your question??

That is going to be rather difficult unless you have some other way of getting the current date and time. According to MSDN:
A single tick represents one hundred nanoseconds or one ten-millionth of a second. There are 10,000 ticks in a millisecond.
The value of this property represents the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001, which represents DateTime.MinValue. It does not include the number of ticks that are attributable to leap seconds.
Now, if you know the current date and time, you can calculate how many days have passed since January 1, 0001 and use that to calculate the number of ticks.

I understand you dont want the hour parts of the date. If you use Date, then you only get the day (for example: 01/01/2012 00:00:00)
long ticks = new DateTime(2012, 1, 31).Date.Ticks;
And with any DateTime object already created is the same of course.
long ticks = dateObject.Date.Ticks;

You already have the answer there in your post:
long ALL_Ticks = DateTime.Now.Ticks;
// that's the ticks (from DateTime.MinValue) until 'now' (this very moment)
long ticks = new DateTime(2012, 1, 31).ToLocalTime().Ticks;
// or
long ticks = DateTime.Now.Date.Ticks;
// that's the ticks until the beginning of today
long yearmonthticks = new DateTime(2012, 1, 1).ToLocalTime().Ticks;
// that's the ticks until the beginning of the month
// etc..., the rest is simple subtractions
Since your question doesn't specify any reason not to use the DateTime constructor, this is the best solution for what seems like your problem.

I had a use case where I couldn't use DateTime but needed Years/Months from Ticks.
I used the source behind DateTime to figure out how. To go the other way you can look at the constructor, one of which calls the following code.
private static long DateToTicks(int year, int month, int day) {
if (year >= 1 && year <= 9999 && month >= 1 && month <= 12) {
int[] days = IsLeapYear(year)? DaysToMonth366: DaysToMonth365;
if (day >= 1 && day <= days[month] - days[month - 1]) {
int y = year - 1;
int n = y * 365 + y / 4 - y / 100 + y / 400 + days[month - 1] + day - 1;
return n * TicksPerDay;
}
}
throw new ArgumentOutOfRangeException(null, Environment.GetResourceString("ArgumentOutOfRange_BadYearMonthDay"));
}
This can be found in link below, of course you will need to re-write to suit your needs and look up the constants and IsLeapYear function too.
https://referencesource.microsoft.com/#mscorlib/system/datetime.cs,602

Subtracting TimeSpan from date

I want to subtract a time-span from a date-time object using a 30-day month and ignoring leap years etc.
Date is 1983/5/1 13:0:0 (y/m/d-h:m:s)
Time span is 2/4/28-2:51:0 (y/m/d-h:m:s)
I can use DateTime and TimeSpan objects to do this, after converting years and months of the time-span to days (assuming a 30 day month and a ~364 day year).
new DateTime(1981,5,1,13,0,0).Subtract(new TimeSpan(878,13,51,0));
With this i get the result:
{12/4/1978 11:09:00 PM}
Above answer obviously doesn't ignore the factors i want ignored and gives me an accurate answer. But in this case that's not what i want so i wrote the below code.
public static CustomDateTime operator -(CustomDateTime DT1,CustomDateTime DT2)
{
CustomDateTime retVal = new CustomDateTime();
try
{
const int daysPerYear = 364.25;
const int monthsPerYear = 12;
const int daysPerMonth = 30;
const int hoursPerDay = 24;
const int minutesPerHour = 60;
retVal.Minute = DT1.Minute - DT2.Minute;
if (retVal.Minute < 0)
{
retVal.Minute += minutesPerHour;
DT1.Hour -= 1;
}
retVal.Hour = DT1.Hour - DT2.Hour;
if (retVal.Hour < 0)
{
retVal.Hour += hoursPerDay;
DT1.Day -= 1;
}
retVal.Day = DT1.Day - DT2.Day;
if (retVal.Day < 0)
{
retVal.Day += daysPerMonth;
DT1.Month -= 1;
}
retVal.Month = DT1.Month - DT2.Month;
if (retVal.Month < 0)
{
retVal.Month += monthsPerYear;
DT1.Year -= 1;
}
retVal.Year = DT1.Year - DT2.Year;
}
catch (Exception ex) { }
return retVal;
}
Then i get:
1981/0/3-10:9:0
This is pretty close to what i'm after except i shouldn't get 0 for month and year should be 1980. Any kind of help is appreciated.
Just to make things clear again; in this context I have to use a 30-day month and ignore leap-years, different numbers of months, etc. Its a weird thing to do, i know. So I'm pretty much after a 'wrong answer' as opposed to the exact answer given by the managed classes.

If you're estimating a month at 30 days, of course your math will be off. When you subtract 878 days from 5/1/1981, .Net is giving you the exact difference, not an estimate, and this difference accounts for leap years, if there are any. The error is not in the Subtract(...) method - it is in your own "manual" calculation.
DateTime dt = new DateTime(1981, 5, 1, 13, 0, 0);
TimeSpan t = new TimeSpan(878, 13, 51, 0);
dt.Ticks
624931668000000000
t.Ticks
759090600000000
dt.Ticks - t.Ticks
624172577400000000
new DateTime(dt2)
{12/4/1978 11:09:00 PM}
Date: {12/4/1978 12:00:00 AM}
Day: 4
DayOfWeek: Monday
DayOfYear: 338
Hour: 23
Kind: Unspecified
Millisecond: 0
Minute: 9
Month: 12
Second: 0
Ticks: 624172577400000000
TimeOfDay: {23:09:00}
Year: 1978
These are the total ticks since the epoch. Do this math, then convert back into a datetime.
Also: correct your math. 878 days is 2 years and 148 days. 5/1/1981 is the 121st day of the year, so subtract 120 to get Jan 1, 1979. This leaves 28 days. Start counting backwards from the end of 1978, and you get very close to the .Net answer. Your own answer isn't anywhere close.
EDIT based on feedback
// zh-Hans is a chinese culture
CultureInfo ci = CultureInfo.GetCultureInfo("zh-Hans");
DateTime dt = new DateTime(1981, 5, 1, 13, 0, 0, ci.Calendar);
TimeSpan t = new TimeSpan(878, 13, 51, 0);
Please note that you are still subtracting 878 days. The length of a month would be irrelevant in that case based on the Julian calendar. You will probably need to find the correct culture code for your particular calendar, then try this. However, with this calendar, I still arrive at the same answer above.
Beyond doing this, I am unsure how else to do the math. If you can provide a link to how you are doing it by hand, I can help code it for you.
EDIT 2
I understand now. Try this:
DateTime dt = new DateTime(1981, 5, 1, 13, 0, 0, ci.Calendar);
int years = 878 / 365;
int remainingDays = 878 % 365;
int months = remainingDays / 30;
remainingDays = remainingDays % 30;
TimeSpan t = new TimeSpan(years * 365 + months * 30 + remainingDays);
DateTime newdate = dt.Subtract(t);

You cannot assume a 30-day month. You are specifying that you want to subtract 878 days. The managed classes (I'm assuming you mean managed when you say native) are designed to factor in leap-years, different numbers of months, etc.
Using the managed classes will not give you a 0 for a month.