# Time#round

**URL:** <https://www.ruby-forum.com/t/time-round/184969>\
**Category:** Development\
**Created:** [March 11, 2010, 7:10am UTC](https://www.ruby-forum.com/t/time-round/184969 "2010-03-11T07:10:03Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [March 11, 2010, 7:10am UTC](https://www.ruby-forum.com/t/time-round/184969/1 "2010-03-11T07:10:03Z")

</div>

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e$B$A$g$&$Ie(B [ruby-core:28602] e$B$K$b$"$j$^$7$?$,!“e(B  
Time e$B%\*%V%8%’%/%HFb$K8m:9$r4^$`CM$rF~$l$F$7$^$&$3$H$,$”$j$^$9!#e(B

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strftime e$B$Ne(B %N e$B$O!"\>.?tE@0J2\<$NIC?t$rI=\<($9$k$b$N$J$N$G!"e(B  
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%N e$B$@$1$G$J$/!"e(Busec e$B$de(B nsec  
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e$B$3$3$G!“e(BTime#round e$B$r;H$&$H!”\>.?tE@0J2\<$r;M\<N8^F~$7$?e(B  
Time e$B%\*%V%8%’%/%H$rF@$i$l$^$9!#e(B

% ./ruby -e ’  
t = Time.utc(1999,12,31, 23,59,59,876543)  
p t, t.subsec  
t = t.round  
p t, t.subsec’  
1999-12-31 23:59:59 UTC  
(876543/1000000)  
2000-01-01 00:00:00 UTC  
0

e$B$^$?!“e(BInteger#round  
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strftime e$B$NA0$Ke(B round(3) e$B$r8F$V$3$H$G\<B8=$G$-$^$9!#e(B

% ./ruby -e ’  
t = Time.utc(1999,12,31, 23,59,59,876543)  
p t, t.subsec, t.strftime("%T.%3N")  
t = t.round(3)  
p t, t.subsec, t.strftime("%T.%3N")  
’  
1999-12-31 23:59:59 UTC  
(876543/1000000)  
“23:59:59.876”  
1999-12-31 23:59:59 UTC  
(877/1000)  
“23:59:59.877”

e$B$I$&$G$7$g$&e(B?

# % svn diff --diff-cmd diff -x ‘-u -p’ Index: time.c

— time.c (revision 26871)  
+++ time.c (working copy)  
@@ -2997,6 +2997,64 @@ rb\_time\_succ(VALUE time)

#define time\_succ rb\_time\_succ

+/\*

- 
  - call-seq:

- 
  - time.round([ndigits]) =\> new\_time

- 
  - 

- 
  - Rounds sub seconds to a given precision in decimal digits (0  
digits by default).

- 
  - It returns a new time object.

- 
  - _ndigits_ should be zero or positive integer.

- 
  - 

- 
  - 

```
require 'time'

```

- 
  - 

- 
  - 

```
t = Time.utc(1999,12,31, 23,59,59)

```

- 
  - 

```
p((t + 0.4).round.iso8601(3)) #=> "1999-12-31T23:59:59.000Z"

```

- 
  - 

```
p((t + 0.49).round.iso8601(3)) #=> "1999-12-31T23:59:59.000Z"

```

- 
  - 

```
p((t + 0.5).round.iso8601(3)) #=> "2000-01-01T00:00:00.000Z"

```

- 
  - 

```
p((t + 1.4).round.iso8601(3)) #=> "2000-01-01T00:00:00.000Z"

```

- 
  - 

```
p((t + 1.49).round.iso8601(3)) #=> "2000-01-01T00:00:00.000Z"

```

- 
  - 

```
p((t + 1.5).round.iso8601(3)) #=> "2000-01-01T00:00:01.000Z"

```

- 
  - 

- 
  - 

```
t = Time.utc(1999,12,31, 23,59,59)

```

- 
  - 

```
p (t + 0.123456789).round(4).iso8601(6) #=>

```

“1999-12-31T23:59:59.123500Z”

- \*/
- 

+static VALUE  
+time\_round(int argc, VALUE \*argv, VALUE time)  
+{

- VALUE ndigits, v, a, b, den;
- long nd;
- struct time\_object \*tobj;
- 
- rb\_scan\_args(argc, argv, “01”, &ndigits);
- 
- if (NIL\_P(ndigits))
- 

```
   ndigits = INT2FIX(0);

```

- else
- 

```
   ndigits = rb_to_int(ndigits);

```

- 
- nd = NUM2LONG(ndigits);
- if (nd \< 0)
- rb\_raise(rb\_eArgError, “negative ndigits given”);
- 
- GetTimeval(time, tobj);
- v = rb\_time\_unmagnify(tobj-\>timexv);
- 
- a = INT2FIX(1);
- b = INT2FIX(10);
- while (0 \< nd) {
- 

```
   if (nd & 1)

```

- 

```
       a = mul(a, b);

```

- 

```
   b = mul(b, b);

```

- 

```
   nd = nd >> 1;

```

- }
- den = quo(INT2FIX(1), a);
- v = mod(v, den);
- if (lt(v, quo(den, INT2FIX(2))))
- 

```
   return time_add(tobj, v, -1);

```

- else
- 

```
   return time_add(tobj, sub(den, v), 1);

```

+}

/\*

- call-seq:  
@@ -3918,6 +3976,8 @@ Init\_Time(void)  
rb\_define\_method(rb\_cTime, “-”, time\_minus, 1);

- rb\_define\_method(rb\_cTime, “round”, time\_round, -1);
- rb\_define\_method(rb\_cTime, “sec”, time\_sec, 0);  
rb\_define\_method(rb\_cTime, “min”, time\_min, 0);  
rb\_define\_method(rb\_cTime, “hour”, time\_hour, 0);  
Index: test/ruby/test\_time.rb  
===================================================================  
— test/ruby/test\_time.rb (revision 26871)  
+++ test/ruby/test\_time.rb (working copy)  
@@ -576,4 +576,37 @@ class TestTime \< Test::Unit::TestCase  
assert\_kind\_of(Rational, Time.new(2000,1,1,0,0,Rational(4,3)).to\_r)  
assert\_kind\_of(Rational, Time.utc(1970).to\_r)  
end
- 
- def test\_round
- t = Time.utc(1999,12,31, 23,59,59)
- t2 = (t+0.4).round
- assert\_equal([59,59,23, 31,12,1999, 5,365,false,“UTC”], t2.to\_a)
- assert\_equal(0, t2.subsec)
- t2 = (t+0.49).round
- assert\_equal([59,59,23, 31,12,1999, 5,365,false,“UTC”], t2.to\_a)
- assert\_equal(0, t2.subsec)
- t2 = (t+0.5).round
- assert\_equal([0,0,0, 1,1,2000, 6,1,false,“UTC”], t2.to\_a)
- assert\_equal(0, t2.subsec)
- t2 = (t+1.4).round
- assert\_equal([0,0,0, 1,1,2000, 6,1,false,“UTC”], t2.to\_a)
- assert\_equal(0, t2.subsec)
- t2 = (t+1.49).round
- assert\_equal([0,0,0, 1,1,2000, 6,1,false,“UTC”], t2.to\_a)
- assert\_equal(0, t2.subsec)
- t2 = (t+1.5).round
- assert\_equal([1,0,0, 1,1,2000, 6,1,false,“UTC”], t2.to\_a)
- assert\_equal(0, t2.subsec)
- 
- t2 = (t+0.123456789).round(4)
- assert\_equal([59,59,23, 31,12,1999, 5,365,false,“UTC”], t2.to\_a)
- assert\_equal(Rational(1235,10000), t2.subsec)
- 
- off = 0.0
- 100.times {|i|
- 

```
 t2 = (t+off).round(1)

```

- 

```
 assert_equal(Rational(i % 10, 10), t2.subsec)

```

- 

```
 off += 0.1

```

- }
- end  
end

---

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [March 11, 2010, 8:47am UTC](https://www.ruby-forum.com/t/time-round/184969/2 "2010-03-11T08:47:47Z")

</div>

e$B$^$D$b$He(B e$B$f$-$R$m$G$9e(B

In message “Re: [ruby-dev:40595] Time#round”  
on Thu, 11 Mar 2010 15:09:45 +0900, Tanaka A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
writes:

|e$BA0$K$A$g$C$H=q$-$^$7$?$,!"e(BTime#round e$B$rDI2C$9$k$N$O$I$&$G$7$g$&!#e(B  
|e$B$3$l$O!"ICL$K~$N;~9o$r4]$a$k%a%=%C%I$G$9!#e(B

e$B$$$$$s$8$c$J$$$G$7$g$&$+!#e(B