I know this is probably a pretty simple question, but i am trying to write a function that returns a bool value of "true" if a date passed is in the future, like this:
bool IsFutureDate(System.DateTime refDate)
{
if (refDate > DateTime.Now) // This doesn't seem to work
return true;
return false;
}
Anyone tell me who to write a function like this that actually works?
Thanks
The only thing I can think of is you might get undefined behaviour if refDate == today.
DateTime.Now includes the time. If refDate if for say today at 3:00 and you run it at 2:00 it will return true. If you run at 4:00 it will return false.
Compare it to DateTime.Today and that will just return the date, preventing the time of day influencing it.
Other than that it should all be fine..
DateTime handling is always tricky.
I have summarized what's been mentioned so far and made this post Community Wiki.
Time Zone Handling
static bool IsFutureDateTime(DateTime dateTime) {
// NOTE: ToUniversalTime() treats DateTimeKind.Unspecified as local time. We
// therefore insist that the input kind is always specified.
if (dateTime.Kind == DateTimeKind.Unspecified) {
string msg = "dateTime.Kind must not be DateTimeKind.Unspecified.";
throw new ArgumentException(msg, "dateTime");
}
return dateTime.ToUniversalTime() > DateTime.UtcNow;
}
Comparing Dates Only
static bool IsFutureDate(DateTime date) {
return date.Date > DateTime.Today;
}
bool IsFutureDate(DateTime refDate) {
DateTime today = DateTime.Today;
return (refDate.Date != today) && (refDate > today);
}
The TimeSpan structure is helpful:
http://msdn.microsoft.com/en-us/library/system.timespan.aspx
How precise do you need it to be? Down to the millisecond?
Related
I have a database table with columns of type dateTime.
Now I need to see if there already is a row with today's date, but I don't know how to compare the column with the current date without the hour, minutes, seconds.
Basically I have 2022-02-04 14:06:21.080 and I need to check if there is a row created on 2022-02-04.
I'm looking for something like
if (db.dates.Where(x => x.SentDate == Date.Now).Count() > 0)
{
// Do something
}
else
{
// Do something else
}
I only need to see if it has a date from today it doesn't matter what time it was created.
Any help is much appreciated!
If you're filtering for a specific date you can use the DateTime.Date property on both DateTime objects. This will compare the date component of the DateTime:
db.dates.Where(x => x.SentDate.Date == DateTime.Now.Date)
// or
db.dates.Where(x => x.SentDate.Date == DateTime.Today)
If you have a nullable DateTime? column, then you use the Value property along with HasValue:
db.dates.Where(x => x.SentDate.HasValue
&& x.SentDate.Value.Date == DateTime.Today)
Unfortunately, expression trees do not support the null propagation operator ?. so we need to use the above method instead.
DateTime.Date can also be used for date ranges, but take care with the upper bound.
PS: DateTime.Today is the same as DateTime.Now.Date
You can check a date range
var today = DateTime.Today;
var tomorrow = today.AddDays(1);
if(db.dates.Where(x => x.SentDate >= today && x.SentDate < tomorrow) ...
The DateTime.Today Property gets the current date with the time component set to 00:00:00.
You can check a date range
var today = DateTime.Today;
var tomorrow = today.AddDays(1);
if(db.dates.Where(x => x.SentDate >= today && x.SentDate < tomorrow) ...
The DateTime.Today Property gets the current date with the time component set to 00:00:00.
Note that we test the lower bound with >= today (with today meaning today at 00:00:00) but the upper one with < tomorrow, since we do not want to include tomorrow at 00:00:00.
Another way is to convert the dates to string and compare.
if(db.dates.Any(m=>m.SentDate.ToString("d") == DateTime.Now.ToString("d"))){
//Do something else
}
else
{
// Do something else
}
If you use MS SQL Server you can use a special function EF.Functions.DateDiff that was created to be used with EF. It can count datetime difference from seconds to months. DateDiffDay is used to count days.
var dateTimeNow = DateTime.Now;
if (db.dates.Any(x => EF.Functions.DateDiffDay(x.SentDate , dateTimeNow) == 0 )
{
// ... there are today's dates
}
// ...
Can you help me in removing the time in my code or rather correct my code for possible errors.
Thanks. Here's my code and ill state the error later.
else if (this.dateTimePicker1.Value != DateTime.Now)
{
this.chkBxLessNinety.Enabled = false;
string dateInString = Convert.ToString(Convert.ToDateTime(_dr[4]));
DateTime startdate = DateTime.Parse(dateInString);
DateTime datelimit = startdate.AddDays(90);
//string date = Convert.ToString(Convert.ToDateTime(datelimit.Date).ToString("mm/dd/yyyy"));
string mydate1 = this.dateTimePicker1.Value.ToShortDateString();
if (mydate1 > datelimit)
{
MessageBox.Show("Cannot Sync data more or equal to 90 days");
}
else
{
}
the line if (mydate1 > datelimit) shows an error which says > cannot be applied as operand of type string an datetime.
Please help.
Thanks in advance.
You want to compare DateTimes with each other. Since you want to exclude the time portion then the Date property will make both dates at midnight hour.
DateTime mydate1 = this.dateTimePicker1.Value;
if (mydate1.Date > datelimit.Date)
{
MessageBox.Show("Cannot Sync data more or equal to 90 days");
}
Just remove .ToShortDateString()
And also:
string dateInString = Convert.ToString(Convert.ToDateTime(_dr[4]));
DateTime startdate = DateTime.Parse(dateInString);
Don't convert from DateTime to string and then back to DateTime, it's pointless
You can't use the > to compare a string and a DateTime. Instead, you should replace
string mydate1 = this.dateTimePicker1.Value.ToShortDateString();
with
DateTime mydate1 = this.dateTimePicker1.Value;
This way, you'll be comparing things of the same type (DateTime).
I want to compare two dates; one taken from a Date column in SQL and the current DateTime.Now. The former has no time portion (technically it does, but it's zeroed out) and of course the later will have the current time to the nearest millisecond. Here is what I am doing now, and it seems inefficient:
DateTime compareDate = Convert.ToDateTime(string.Format("{0:M/d/yyyy}", DateTime.Now));
if (myObj.EndDate < compareDate)
{
myObj.Status = "PAST";
}
else if (myObj.StartDate <= compareDate && myObj.EndDate >= compareDate)
{
myObj.Status = "ACTIVE";
}
else
{
myObj.Status = "PENDING";
}
Is there a better way to strip time off a DateTime variable?
Yes, use the Date property of the DateTime structure, or just use DateTime.Today.
e.g.
DateTime compareDate = DateTime.Now.Date
or
DateTime compareDate = DateTime.Today
Use the property "Date" on the the DateTime variable you want to strip the time from.
var pureDate = DateTime.Now.Date;
I have a DateTime object that I'd like to check and see if it falls within the last 24 hours.
I did something like this but its wrong:
myDateTime > DateTime.Now.AddHours(-24) && myDateTime < DateTime.Now
where did I go wrong?
There is nothing wrong with the code that you posted, so whatever you did wrong is somewhere else in the code.
I only see two minor flaws in the code, but they only affect corner cases:
You should avoid getting the DateTime.Now property repeatedly in the code. Its value changes, so you may get inconsistent results in some cases when the values changes from one use to the next.
To get a time interval you would usually pair one inclusive and one exclusive operator, like > and <=, or >= and <. That way you can check for intervals next to each other, like 0 - 24 hours and 24 - 28 hours, without getting a gap or an overlap.
DateTime now = DateTime.Now;
if (myDateTime > now.AddHours(-24) && myDateTime <= now)
Only get DateTime.Now once within the function - otherwise the value might change.
Use <=, not <. if you check a microsecond after the time has been set, it will still be equal to DateTime.Now. I actually ran into this in production code where imports wouldn't show up in a different query that checked < because the import was too fast!
Use this code:
DateTime now = DateTime.Now;
DateTime yesterday = now.AddDays(-1);
if (myDateTime > yesterday && myDateTime <= now) {
...
}
Learning from both the above answers and also to improve the readability of the code we can use a method like this.
using System;
public class Program
{
public static void Main()
{
DateTime myDateTime = DateTime.Parse("2021-08-25T20:20:19.5540211");
DateTime now = DateTime.Now;
DateTime yesterday = now.AddHours(-24);
if (IsBewteenTwoDates(myDateTime, yesterday, now))
{
Console.WriteLine("this date ({0}) is between {1} & {2}", myDateTime, yesterday, now);
}
else
{
Console.WriteLine("this date ({0}) is not between {1} & {2}", myDateTime, yesterday, now);
}
}
// Checks if the DateTime object dt is between start and end DateTime.
public static bool IsBewteenTwoDates(DateTime dt, DateTime start, DateTime end)
{
return dt >= start && dt <= end;
}
}
Check the fiddle here.
DateTime dt=Convert.ToDateTime(data);
if ((dt.Year == DateTime.Now.Year)
&& (dt.Month == DateTime.Now.Month)
&& (dt.Day == DateTime.Now.Day))
lblDate.Text = "Today";
This code too lazy
How to compare 2 date variables the easy way?
How to get the difference of 2 date variables in minutes?
For the first question:
In general:
if (first.Date == second.Date)
To check whether a DateTime is "today"
if (dateTime.Date == DateTime.Today)
Note that this doesn't take any time zone issues into consideration... What do you want to happen if the other DateTime is in UTC, for example?
I'm not sure what you mean by the second question. Could you elaborate? You can do:
TimeSpan difference = first - second;
if that's any help... look at the TimeSpan documentation for more information about what's available. For instance, you may mean:
double minutes = (first - second).TotalMinutes;
but you may not...
1. DateTime.Equals(DateTime dt1, DateTime dt2)
DateTime dt=Convert.ToDateTime(data);
if (dt.Date == DateTime.Today)
lblDate.Text = "Today";
you can use subtract Method
DateTime dt=Convert.ToDateTime(data);
id(dt==DateTime.Now)
{
lblDate.Text = "Today";
}
1. if (dt.Date == DateTime.Today)
2. (first - second).TotalMinutes