date-arithmetic

问题 This question already has answers here : Why does JavaScript handle the plus and minus operators between strings and numbers differently? (7 answers) Closed 4 years ago . I read a book about operators in Javascript, and this confused me. console.log("5"+1); This would make "5" as a string. So the result would be 51 . console.log("5"-1); This result would be 4 . I know it converts "5" to 5 , but why it isn't shown undefined as "a string minus a number"? Update: So how about other languages?

问题 Let's suppose that today is Wednesday. I can break an NSDate down into NSDateComponents , but I need to find the NSDate with the next upcoming Monday. If today is Monday, then the next upcoming Monday is today. What's the right way to achieve this? 回答1: You can use nextDateAfterDate: method on NSCalendar object to achieve this, let now = Date() // today var matchingComponents = DateComponents() matchingComponents.weekday = 2 // Monday let comingMonday = Calendar.current.nextDate(after: now,

问题 Today, I've encountered an unexplainable result in PostgreSQL 9.6 while running this query: SELECT age('2018-06-30','2018-05-19') AS one, age('2018-07-01','2018-05-20') AS two; Expected results for both columns: 1 mon 11 days . However, only for the interval from 2018-05-19 to 2018-06-30, I get what I expect, while for 2018-05-20 till 2018-07-01 I'll get one day more: 1 mon 12 days I don't get why this is the case and in my understanding, between 2018-05-20 2018-07-01 is just an interval of 1

问题 I have a search button, when the user clicks the search button the search() method is get called. I need to calculate the how much time it took to display the result to the user as we see in the google search. This is my code. SimpleDateFormat sdfDate = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String strDate; def startTime() { Calendar cal = Calendar.getInstance(); System.out.println("Current milliseconds since 13 Oct, 2008 are :" + cal.getTimeInMillis()); long startTime=cal

问题 I have to calculate all the invoices which have been paid in the first 'N' days of a month. I have two tables . INVOICE: it has the invoice information. The only field which does matter is called 'datePayment' . HOLYDAYS: It is a one column table. Entries at this table are of the form "2009-01-01", 2009-05-01" and so on. I should consider also Saturdays and Sundays (this might be not a problem because I could insert those days at the Hollidays table in order to consider them as hollidays if

问题 In my PHP code I have a date in my variable "$postedDate". Now I want to get the date after 7 days, 15 days, one month and 2 months have elapsed. Which date function should I use? Output date format should be in US format. 回答1: Use strtotime. $newDate = strtotime('+15 days',$date) $newDate will now be 15 days after $date. $date is unix time. http://uk.php.net/strtotime 回答2: try this $date = date("Y-m-d");// current date $date = strtotime(date("Y-m-d", strtotime($date)) . " +1 day"); $date =

问题 PHP provides ways to get the number of the current day of the month (date('j')) as well as the number of the current day of the year (date('z')). Is there a way to get the number of the current day of the current quarter? So right now, August 5, it is day 36 of the third quarter. If there is no standard way of calculating this, does anyone have a (prefereably PHP-based) algorithm handy? 回答1: How about: $curMonth = date("m", time()); $curQuarter = ceil($curMonth/3); 回答2: I wrote a class with

问题 I'm trying to understand the floating point arithmetic behind this simple example. Both codes are arithmetically equivalent in theory, but obviously a series of additions adds more error than a simple multiplication. s=0.0 for i in range(10): s += 0.1 print(s) print('%.30f' % s) 0.9999999999999999 0.999999999999999888977697537484 but: s=0.1 s *= 10 print(s) print('%.30f' % s) 1.0 1.000000000000000000000000000000 I would like to understand what is going on behind the scenes. I understand that

问题 I am trying to add months to an existing date in SQL. The new column displayed will have a followup column instead of a days column. Im getting an error in the select statement.can u help? Create table auctions( item varchar2(50), datebought date, datesold date, days number ); Insert into auctions values (‘Radio’,’12-MAY-2001’,’21-MAY-2001’,9); Select item,datebought,datesold,ADD MONTHS(datesold,3)”followup” from auctions; 回答1: Your usage of the add_months() function is incorrect. It's not

问题 This should be simple, but it's proving challenging for me. I'd like to know the best approach to calculating the difference in seconds between [NSDate date] and a future event x seconds from that time. There are several different types of event, and each event may occur several times a day, and at different times, depending what day of the week it happens to be. What I am trying to do is have the user select an event type from a picker and then set an alarm in Notification Center for the