Develop Reference

Change the time forward

I am getting dates from the database and for each date I want to change the time forward starting from the DateTime that was obtained from the database until I get to a given Fixed Time (Y). However, (Y) might be in the next day.
For example if the date from the database is [7/6/2017 5:00:00 AM] and the given Fixed Time is 10:00 PM then I want to get [7/6/2017 10:00:00 PM].
However if the fixed time is 02:00 AM then I want to get [7/7/2017 02:00:00 AM] (notice that the date has increased by one)
Note: The code is running, but I modified the code to make it shorter and make more sense. Thus, there might be syntax or spelling mistakes.
My first solution was something like this:
private DateTime setTimeForeward(DateTime date) {
DateTime today = DateTime.ParseExact(FixedTime, "hh:mm tt", CultureInfo.InvariantCulture);
TimeSpan difference = today.TimeOfDay - date.TimeOfDay;
return date + difference;
}
That didn't work as expected when the fixed time is 02:00 AM. The difference becomes negative( it doesn't go around the clock) and the date will be [7/6/2017 02:00:00 AM].
I ended up with the following code
private DateTime setTimeForeward(DateTime date) {
DateTime today = DateTime.ParseExact(FixedTime "hh:mm tt", CultureInfo.InvariantCulture);
TimeSpan difference = today.TimeOfDay - date.TimeOfDay;
if (difference.Hours < 0) {
difference += new TimeSpan(24, 0, 0);
}
return date + difference;
}
I am not sure if my function is logically correct and I feel like I am overthinking it. Also,I am not sure if there's a better way or a built in function that does what I want for me. Basically, I am looking for a correct and an elegant solution.
Thank you very much in advanced.

In this method, I'm using DateTime fixedTime to represent a time. I don't really care about it's Day, Month, and Year values.
static DateTime GetClosingTime(DateTime fixedTime, DateTime dbTime)
{
var cutoff = new DateTime(dbTime.Year, dbTime.Month, dbTime.Day, fixedTime.Hour, fixedTime.Minute, fixedTime.Second);
if (dbTime < cutoff)
return cutoff;
else
{
cutoff = cutoff.AddDays(1);
return cutoff;
}
}
Here's calling it with your provided example input.
var FixedTime10PM = new DateTime(1, 1, 1, 22, 0, 0);
var FixedTime02AM = new DateTime(1, 1, 1, 2, 0, 0);
var dbTime = new DateTime(2018, 6, 20, 5, 0, 0);
var dt1 = GetClosingTime(FixedTime10PM, dbTime);
var dt2 = GetClosingTime(FixedTime02AM, dbTime);
Console.WriteLine(dt1.ToLongDateString() + " " + dt1.ToLongTimeString());
Console.WriteLine(dt2.ToLongDateString() + " " + dt2.ToLongTimeString());
And here's my output:
EDIT:
Simplified method based on suggestions in comments:
static DateTime GetClosingTime(DateTime fixedTime, DateTime dbTime)
{
var cutoff = new DateTime(dbTime.Year, dbTime.Month, dbTime.Day, fixedTime.Hour, fixedTime.Minute, fixedTime.Second);
return dbTime < cutoff ? cutoff : cutoff.AddDays(1);
}

Your logic is almost right but you shouldn't be checking for difference.Hours because there might be a difference in minutes (or even seconds if you changed the format later).
I adjusted your function and changed some variable names to make them easier to follow:
private DateTime SetTimeForward(DateTime originalDate)
{
TimeSpan newTime = DateTime.ParseExact(FixedTime,
"hh:mm tt",
CultureInfo.InvariantCulture).TimeOfDay;
TimeSpan diff = newTime - originalDate.TimeOfDay;
if (diff.Ticks < 0)
diff = diff.Add(new TimeSpan(24, 0, 0));
return originalDate.Add(diff);
}
Some remarks:
If your FixedTime is really fixed, you might want to store it directly as a TimeSpan so you don't have to parse it every time.
If you parse the FixedTime because it's changeable, you might pass it as a second argument instead:
private DateTime SetTimeForward(DateTime originalDate, string fixedTime)
Or:
private DateTime SetTimeForward(DateTime originalDate, TimeSpan newTime)
The current implementation does not change the date value if the newTime is equal to originalDate.TimeOfDay. I.E., If the originalDate is 7/6/2017 2:00 AM and the FixedTime/newTime is 02:00 AM, the returned date will be equal to the originalDate. If that's not your desired behavior, you might change diff.Ticks < 0 to diff.Ticks <= 0.

Slightly different approach:
private DateTime setTimeForeward(DateTime date)
{
var targetTimeOfDay = TimeSpan.ParseExact(FixedTime, "hh:mm tt", CultureInfo.InvariantCulture);
if (targetTimeOfDay < date.TimeOfDay)
{
date = date.AddDays(1);
}
return date.Date + targetTimeOfDay;
}
I'm getting target time as TimeSpan from the beginning instead of creating DateTime and getting TimeOfDay (which is TimeSpan).
Then I check if the target time of day is lower than time to be modified and if it is I add one day.
I use date.Date + targetTimeOfDay as return value as date.Date will return date with time set to 00:00 and adding target time to it will already set the target hour without calculating the difference.

How can I prevent negative time in using military time format

when my starttime = "19:00" PM then my endtime ="01:30" AM
the answer is negative , how can i prevent negative result in time?
string startime = record.TimeStart;
string endtime = record.TimeFinish;
TimeSpan span = DateTime.Parse(endtime).Subtract(DateTime.Parse(startime));
string hours_spent = string.Format(
"{0:D2}:{1:D2}:{2:D2}",
span.Hours, span.Minutes, span.Seconds);

You are crossing midnight, so the actual comparison is (using today's date as an example):
[2015-10-12 01:30] - [2015-10-12 19:00]
which is -17 hrs and 30 minutes. If you want to convert that to a positive time then either add a date component or add 24 hours to the time span:
if(span.Hours < 0)
span = span.AddDays(1);

Add one day to endtime if it (or more precisely, its time component) is earlier than starttime's. Something like this:
var startDateTime = DateTime.Parse(starttime).Time;
var endDateTime = DateTime.Parse(endtime).Time;
if (endDateTime < startDateTime)
{
endDateTime += TimeSpan.FromDays(1);
}
TimeSpan timeSpent = endDateTime - startDateTime;

Timespan between (2) other Timespan when adding / subtracting minutes C#

Everything works with the exception if I pass in "15 minutes". I receive no errors, it's just that my where clause isn't working 100%. This is b/c I pass in time in 15 minute intervals.
Example:
Object 1 has a time of 00:20 (12:20 am) (24hr format)
Object 2 has a time of 02:15 (02:15 am) (24hr format)
The parsedTime param is a javascript 24hr format time - in this example is comes in as "00:15".
The problem is when I subtract the -30 minutes from the parsedTime, it puts it at 23:45, and therefore never gets the "00:20".
LINQ query
DateTime parsedTime = DateTime.ParseExact(time, "HH:mm", CultureInfo.InvariantCulture);
var activities = objects
.Where(x => (x.GetValue<DateTime>("startTime").TimeOfDay
>= parsedTime.AddMinutes(-30).TimeOfDay
&& x.GetValue<DateTime>("startTime").TimeOfDay
<= parsedTime.AddMinutes(30).TimeOfDay))
.ToList();

You just want to see if they're within 30 minutes of each other, right? Try using actual timespans
DateTime startTime;
DateTime parsedTime;
TimeSpan difference = startTime - parsedTime;
return difference.TotalMinutes < 30 && difference.TotalMinutes > -30;

It sounds like you also need to handle time ranges that could span across midnight, as in the 30 minutes that exists between "23:45" and "00:15". Here's how you can do that:
public static TimeSpan GetTimeDifference(string startTimeOfDay, string endTimeOfDay)
{
DateTime startDateTime = DateTime.ParseExact(startTimeOfDay, "HH:mm",
CultureInfo.InvariantCulture, DateTimeStyles.NoCurrentDateDefault);
DateTime endDateTime = DateTime.ParseExact(endTimeOfDay, "HH:mm",
CultureInfo.InvariantCulture, DateTimeStyles.NoCurrentDateDefault);
if (endDateTime >= startDateTime)
{
// values do not cross over midnight
return endDateTime - startDateTime;
}
else
{
// values cross over midnight
return endDateTime - startDateTime + TimeSpan.FromHours(24);
}
}
Or if you prefer something smaller:
public static int GetMinutesDifference(string startTimeOfDay, string endTimeOfDay)
{
DateTime startDateTime = DateTime.ParseExact(startTimeOfDay, "HH:mm",
CultureInfo.InvariantCulture, DateTimeStyles.NoCurrentDateDefault);
DateTime endDateTime = DateTime.ParseExact(endTimeOfDay, "HH:mm",
CultureInfo.InvariantCulture, DateTimeStyles.NoCurrentDateDefault);
return (((int)(endDateTime - startDateTime).TotalMinutes + 1440) % 1440);
}

How to set current time to a value

I was just wondering if there is a way to get the current time and set it into a value.
If its 12:06 AM.. I want to get that time and set it into currentTime.
Example
float currentTime = 0;
currentTime = 12.06;

As others have mentioned, the DateTime class would be ideal for this, and to work out the difference between 2 date/times:
DateTime end = DateTime.Now;
DateTime start = new DateTime(2011, 12, 5, 12, 6,0);
double hours = (end - start).TotalHours;
The subtraction of DateTime objects results in a TimeSpan object that you can use to see the hours/minutes etc.

try DateTime class
DateTime dt = DateTime.Now;

Is this what you're looking for?
DateTime currentTime;
currentTime = DateTime.Now;

Don't use floats or strings. You can do all kinds of cool things using DateTime.
Here's how you'd get the hours that someone worked:
var clockIn = new DateTime(2011,12,4,9,0,0); // December 4th, 9 AM
var clockOut = new DateTime(2011,12,4,17,0,0); // December 4th, 5 PM
var duration = clockOut - clockIn; // TimeSpan
Console.Write(duration.TotalHours); // 8

A few people have mentioned how, but as a 'better' recommendation you should use
DateTime currentTime = DateTime.UtcNow
Otherwise you have issues when the clocks go back, if your timing code is run on those days. (plus it is far easier to alter the UTC time to local time than it is to convert a '1am' to UTC (as there will be two of them when the clocks go back)

Well if you really what it as a float then try:
var currentDate = DateTime.Now;
float currentTime = float.Parse((currentDate.Hour > 12 ? currentDate.Hour -12 :
currentDate.Hour) + "." + currentDate.Minute);
I wouldn't recommend comparing dates or time with floats. A better options would be to use timespans.

You should be using a Timespan instance for time related values, you can use the flexibility to get the required values like
TimeSpan ts = DateTime.Now.TimeOfDay;
ts.ToString("hh:mm") // this could be what you are looking for
You could then use ts.TotalHours which would give you fractional hours (as a double) else you could construct a string specifically using ts.Hours ..ts.Minutes play around and it could be prove useful.

Try the following:
DateTime StartTime=StartTime value;
DateTime CurrentTime=DateTime.Now;
TimeSpan dt = CurrentTime.Subtract(StartTime);
In dt you will get a working time period.

If you want to have the difference between two times, then do this:
DateTime dateOne = DateTime.Parse(enteredTime);
DateTime dateTwo = DateTime.Now;
TimeSpan difference = dateOne - dateTwo;

Time span calculation for hours and minutes in C#

The final result should display the user the time span between the start hour and the end hour.(e.g. start work at 06:30 AM and finished at 18:30 PM, the result to display should be 12 hours).
Now, I have to DateTime parameters; fromTime and toTime
Each DateTime parameter have an hour in 24 hour format, and also might have a minutes value of 30 min.
What I willing to do is to get the time span between those DateTime parameters.
For the hours I used this method:
Public TimeSpan GetHourSpan(DateTime fromTime, DateTime toTime)
{
TimeSpan fromH = TimeSpan.FromHours(fromTime.Hour);
TimeSpan toH = TimeSpan.FromHours(toTime.Hour);
TimeSpan hourTotalSpan = toH.Subtract(fromH);
return hourTotalSpan;
}
This is great, my problem is to get the time span in minutes if there is, and finally add it to the TimeSpan object to display.
If both have 30 min time span in the above way will return 0, and than I have to start check every parameter if it have a value in the min property.
Isn't there an easy way to get time span for hours and min together?

TimeSpan span = toTime - fromTime;
// Split into hours:minutes: span.Hours, span.Minutes
// Total span in hours: span.TotalHours
// Total span in minutes (hours * 60): span.TotalMinutes

If you deduct a DateTime from a DateTime, the result is a a TimeSpan. So you can simply take
TimeSpan result = toTime-fromTime;
int hours = result.Hours;
int minutes = result.Minutes;

TimeSpan span = toTime - fromTime;

public double DurationinMins(DateTime startDt, DateTime endDt)
{
var ts = endDt.Subtract(startDt);
return ts.TotalMinutes;
}