So I'm trying to convert this Excel cell calculation into C#, but I can't really make sense of what it's doing. I read over the EDATE definition and it still doesn't make too much sense.
IF(EDATE(B25,-12)>A25,((EDATE(B25,-12)-A25)/(EDATE(B25,-12)-EDATE(EDATE(B25,-12),-12)))+1,(B25-A25)/(B25-EDATE(B25,-12)))
B25 = End Date
A25 = Start Date
It's essentially trying to calculation a fraction of a year. Should be very easy to do, but I'm not entirely sure what this EDATE thing does.
According to EDATE, you're mostly dealing with 12 months before the End Date (B25).
Given that, this seems to say:
If the start date is more than 12 months before the end date then:
(The amount of time that the start date is prior to the year before the end date divided by one year) + 1
Else:
The amount of time that the start date is prior to the end date divided by one year.
I really don't know how Excel handles date arithmetic or what the point of this function is, but that's my pseudo at a glance.
Really, it's just checking the if condition I mentioned, then offsetting the entire arithmetic by a year if the condition is true.
Edit
Okay, some quick research shows that Excel does date arithmetic purely as days, so then 12/1/1900 - 1/1/1900 = 335 days. Putting a time on either date makes it a fraction of a day.
Given that, this Excel formula appears to attempt to calculate the fractional year difference between the two dates.
This is a rough piece of code that should provide it:
TimeSpan span = endDate.Subtract(startDate);
double years = span.Days / 365.25;
Related
I am setting up a system to gather data from a database based on a user inputted start date and end date. The system will gather data averaged over an interval(1 hour, 6 hours, or one day for example). If the user does not input a start or end date I would like the program to set the start date to the current time minus the interval.
I currently have the user inputting the interval in the following format.
1m = 1 minute
1h = 1 hour
12h = 12 hours
3d = 3 days
So these values are not formatted like datetime. I could take the current datetime and subtract it by either minutes, hours, or days depending on the value appended (splitting on the number), but this would mean many if statements. What I would really like is a method to subtract a datetime by an arbitrary value Does anyone have a better solution?
Instead of providing predefined time intervals (that are implemented e. g. via a separate type/enum), it is much easier to let the user freely specify a TimeSpan.
This has two advantages:
The user is not restricted to predefined intervals
You can subtract the TimeSpan directly from your DateTime.Now
If restriction to limited intervals is a requirement, you can implement this in the view/window. But still this should be a TimeSpan.
This question already has answers here:
Last day of the month in .NET
(5 answers)
Closed 7 years ago.
How can I determine the last day of the month, for the tested month, when the user enters a date into textbox that is further from the available last day for that month? Also how do I feed that back to the user.
When the user enters the date, for example, of April 31, 2015, the date should automatically change to April 30, 2015.
I would like to try doing this using c#
3rd EDIT: The below will get you close to what you're asking for but really just make use of a datepicker control it will help prevent the majority of invalid dates and save you a good amount of development time
2nd EDIT: So TryParse is beneficial because if the date is valid, continue and your done. If you have an invalid date, which TryParse will tell you, then you can compare the value that was input for the day value and see how close it is to the end of the month, i.e. take 31 - 30 = 1, 1 number off so they probably meant 30
EDIT: To answer your question about finding an invalid date check this out: Validate a DateTime in C#
It shows how to detect an invalid date.
To answer your question about how to "guess" which validate date they are closest to I'd say it depends on how you have your date entered. If you do something like have them enter an int value for the day value I'd check to see what the highest day value is for the selected month and then see which one they are closest to (this is just a math operation at this point).
I think this will work
DateTime lastday = new DateTime(DateTime.Today.Year, DateTime.Today.Month, DateTime.DaysInMonth(DateTime.Today.Year, DateTime.Today.Month));
This is an easy way:
//first day of next month
var dt = new DateTime(2015,4,1);
var lastDayOfMonth = dt.AddDays(-1).Day;
As far as delivering a message back to the user, it depends on the environment, technology and preferred approach.
Datediff calculates the no of months between two dates, Is there any function which lets you to calculate the same thing but also includes the current month.
Datediff +1 would give the answer, but just wanted to know if theres any inbuilt method.
Nothing built-in, because it is just that simple to include the current month by adding one, given that you know the diff won't include the current month. It's elegant enough for most developers' needs.
Working on an application where we would like the user to be able to enter incomplete dates.
In some cases there will only be a year - say 1854, or there might be a year and a month, for example March 1983, or there may be a complete date - 11 June 2001.
We'd like a single 'date' attribute/column - and to be able to sort on date.
Any suggestions?
Store the date as an integer -- yyyymmdd.
You can then zero out any month or day component that has not been entered
Year only: 1954 => 19540000
Year & Month: April 2004 => 20040400
January 1st, 2011 => 20110101
Of course I am assuming that you do not need to store any time of day information.
You could then create a struct to encapsulate this logic with useful properties indicating which level of granularity has been set, the relevant System.DateTime, etc
Edit: sorting should then work nicely as well
I can't think of a good way of using a single date field.
A problem you would get if you used January as the default month and 1 as the default day like others have suggested is, what happens when they actually pick January? How would you track if it's a selected January or a defaulted January.
I think you're going to have to store a mask along with the date.
You would only need a bit per part of the date, which would only be 6 bits of data.
M|D|Y|H|Min|S
Month Only 1|0|0|0|0|0 = 32
Year Only 0|0|1|0|0|0 = 8
Month+Year 1|0|1|0|0|0 = 40
AllButMinSec 1|1|1|1|0|0 = 60
You could put this into a Flag Enum to make it easier to use in code.
Well, you could do it via a single column and field that says 'IsDateComplete'.
If you only have the date field, then you'll need to encode the "incompleteness" in the date format itself, such that if the date is, say, < 1900, it's considered "Incomplete".
Personally, I'd go with an field on the side, that marks it as such. Easier to follow, easier to make decisions on, and allows for any dates.
It goes without saying, perhaps, that you can just create a date from DateTime.MinValue and then set what you "know".
Of course, my approach doesn't allow you to "know" what you don't know. (That is, you don't know that they've set the month). You could perhaps use a date-format specifier to mask that, and store it alongside as well, but it's potentially getting cumbersome.
Anyway, some thoughts for you.
One option is to use January as the default month, 1 as the default day, and 1900 or something like that as the default year. Incomplete dates would get padded out with those defaults, and incomplete dates would sort before complete ones in the same year.
Another, slightly more complex option is to use -1 for default day and year, and -1, 'NoMonth', or some such as the default month. Pad incomplete dates as above. This may make sorting a little hard depending on how you do it, but it gives you a way of telling which parts of the date are valid.
I know you'd rather have 1 column but, Instead of a single column one can always have a separate column for day, month and year. Not very difficult to do queries against, and it allways any of the components to be null.
Smehow encoding these states in the datetime itself will be harder to query.
What I did when last solving this problem, was to create a custom date type that kept track of which date parts was actually set and provided conversions to and from a DateTime. For storing in database i used one date field and then one boolean/bit to keep track of which date components that were actually set by the user.
Greetings
I'm trying to do some DateTime math for various time zones and I wanted to take daylight savings into account. Lets say I have a TimeZoneInfo and i've determined the appropriate AdjustmentRule for a given DateTime. Lets also say the particular TimeZoneInfo i'm dealing with is specified as rule.DaylightTransitionStart.IsFixedDateRule == false, so I need to figure out if the given DateTime falls within the start/end TransitionTime.Week values.
This is where I'm getting confused, what is .NET considering as a "week"? My first thought was it probably used something like
DayOfWeek thisMarksWeekBoundaries = Thread.CurrentThread.CurrentUICulture.DateTimeFormat.FirstDayOfWeek;
and went through the calendar assigning days to week, incrementing week every time it crossed a boundary. But, if I do this for May 2010 there are 6 week boundary buckets, and the max valid value for TransitionTime.Week is 5 so this can't be right.
Whats the right way to slice up May 2010?
This article http://msdn.microsoft.com/en-us/library/system.timezoneinfo.transitiontime.isfixeddaterule.aspx shows how to extract the IsFixedDateRule == false, see DisplayTransitionInfo
I finally realized whats going on, I think the property name "Week" is what threw me off. There might be 6 weeks in May (depending on how you count them), but any particular DayOfWeek shows up at most 5 times. The Week property doesn't really refer to what week the DayOfWeek is showing up in, its the nth DayOfWeek for that month--with the magic value 5 meaning its last so either the max n is 4 or 5 for a given month.