How to force user to enter data only once in a day?

Question

UPDATE 2

I've found these but they rely on lat long. Is there any service which can give me result using time zone only as a parameter.

http://www.geonames.org/export/web-services.html#timezone

http://worldtime.io/api/geo

UPDATE 1

I am not using any server. The data is stored in SQLite.

I am creating a health app for Windows Phone 8. In which, user should be allowed to enter certain data on daily basis. So once user has added data for today's date then he/she can enter data on next day only. First I thought to save the last valid date in isolated storage and compare it to current date. If the difference is greater than 24 hours, user should be allowed to enter the data.

Now the problem is if user change the date from his/her phone, DateTime.Now value changes and hence the logic goes wrong. So what should I do to compare the date?

Don't feed the user unless he enters the data once a day. This should work. — Anarion, Oct 15 '13 at 05:07
Why the restriction? More power to the user! Long live the user! — D_Bester, Oct 15 '13 at 05:52
It's not like that. I need to create graph based on date. So ideally user has to enter data one time only in the day. — Farhan Ghumra, Oct 15 '13 at 06:04
Wouldn't a lot of data create better graphs? Just take time elapsed between two measures into account when doing calculations/presentations. — sisve, Oct 15 '13 at 06:19

score 1 · Answer 1 · answered Oct 15 '13 at 05:01

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The last valid date should be decided by the server and not the user. So when the user does an update, you update their last valid date to the current server date, not the user's date. So, before updating, you always compare the user's last valid date (i.e. the server date the last time they updated) to the current server date and see if they're less than 24 hours apart.

answered Oct 15 '13 at 05:01

Hamza Kubba

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I am not using any server. The data is stored in SQLite. I am sorry, I forgot to mention. – Farhan Ghumra Oct 15 '13 at 05:46
Can you use one? Doesn't have to be your server, just has to be any server that returns its own time consistently. – Hamza Kubba Oct 15 '13 at 05:50

score 1 · Answer 2 · answered Oct 15 '13 at 05:12

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Do the validation on both server and client side. Server side validation is must in this case but it is better to have client side validation to reduce unnecessary server calls.

answered Oct 15 '13 at 05:12

Damith

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I am not using any server. The data is stored in SQLite. I am sorry, I forgot to mention. – Farhan Ghumra Oct 15 '13 at 05:44
Just always pass 0, 0 for long/lat? Or any arbitrary location basically, that you always use. – Hamza Kubba Oct 15 '13 at 06:11
But I need to check 24 hour difference according to time zone. – Farhan Ghumra Oct 15 '13 at 06:24

score 1 · Answer 3 · edited May 23 '17 at 10:31

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If the user is online get the time and date from an online service

How to Query an NTP Server using C#

or this: C#: Get NIST Internet Time

 // Convert it to the current timezone if desired
    date = date.ToLocalTime();

National Institute of Standards and Technology (NIST) is the institution that maintains the clocks and makes the time available using Network Time Protocol (NTP). So NIST is the clock and NTP is the manner and method of distributing the time via internet

edited May 23 '17 at 10:31

Community

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answered Oct 15 '13 at 05:48

D_Bester

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Will NIST time gives me date time according to user's timezone? please check update 2. – Farhan Ghumra Oct 15 '13 at 06:06
@Xyroid Did you notice the code: // Convert it to the current timezone if desired if (convertToLocalTime) date = date.ToLocalTime(); Isn't that working for you – D_Bester Oct 15 '13 at 08:03
OK, do you know what's the difference b/w NTP and NIST? – Farhan Ghumra Oct 15 '13 at 09:07

score 0 · Answer 4 · answered Oct 15 '13 at 06:24

If your database is stored on the users device and doesn't use any network connection to some kind of server you simply have to trust your users.

Simply take DateTime.UtcNow.Today for storing the date when the user enters his data. Don't take DateTime.Now or DateTime.UtcNow and check if already 24 hours are gone. In that second case the user won't be able to enter the data at the first day at 11am and the next day at 10am.

Also i would think about not to prohibit entering the data more than once per day. Maybe you should present a message to the users that he already entered some data today and allow him to change the already given data.

If the user really likes to fake some data by changing the datetime of his device, than simply let it do him. If the application works completely locally without any server he only cheats himself.

How to force user to enter data only once in a day?

4 Answers4