Optimize Time.xmlschema by ~4x

[byroot]

It is currentyl fairly slow as it rely on a Regexp match, which isn't very fast an allocates a lot.

Since Ruby 3.2, Time.new(iso_string) is supported, and over 8x faster than Time.xmlschema.

So if we use the regexp with match? to avoid the allocations, and then delegate to .new, we can make Time.xmlschema around 4 times faster:

ruby 4.0.5 (2026-05-20 revision 64336ffd0e) +YJIT +PRISM [arm64-darwin25]
Warming up --------------------------------------
           xmlschema    67.645k i/100ms
            Time.new   531.202k i/100ms
                 opt   263.541k i/100ms
Calculating -------------------------------------
           xmlschema    680.426k (± 0.7%) i/s    (1.47 μs/i) -      3.450M in   5.070197s
            Time.new      5.736M (± 0.9%) i/s  (174.34 ns/i) -     28.685M in   5.000832s
                 opt      2.779M (± 1.1%) i/s  (359.78 ns/i) -     13.968M in   5.025252s

Comparison:
xmlschema:   680426.2 i/s
 Time.new:  5736027.1 i/s - 8.43x  faster
      opt:  2779497.0 i/s - 4.08x  faster

benchmark

```ruby require 'time' require 'benchmark/ips'

class Time
class << self
def baseline(time)
if /\A\s*
(-?\d+)-(\d\d)-(\d\d)
T
(\d\d):(\d\d):(\d\d)
(.\d+)?
(Z|[+-]\d\d(?::?\d\d)?)?
\s*\z/ix =~ time
year = $1.to_i
mon = $2.to_i
day = $3.to_i
hour = $4.to_i
min = $5.to_i
sec = $6.to_i
usec = 0
if $7
usec = Rational($7) * 1000000
end
if $8
zone = $8
off = zone_offset(zone)
year, mon, day, hour, min, sec =
apply_offset(year, mon, day, hour, min, sec, off)
t = self.utc(year, mon, day, hour, min, sec, usec)
force_zone!(t, zone, off)
t
else
self.local(year, mon, day, hour, min, sec, usec)
end
else
raise ArgumentError.new("invalid xmlschema format: #{time.inspect}")
end
end

def match_new(time)
  if /\A\s*
      (-?\d+)-(\d\d)-(\d\d)
      T
      (\d\d):(\d\d):(\d\d)
      (\.\d+)?
      (Z|[+-]\d\d(?::?\d\d)?)?
      \s*\z/ix.match?(time)
    new(time)
  else
    raise ArgumentError.new("invalid xmlschema format: #{time.inspect}")
  end
end

end
end

now = Time.now
iso = now.iso8601(6).freeze
p now
p Time.match_new(iso)

Benchmark.ips do |x|
x.report('xmlschema') { Time.baseline(iso) }
x.report('Time.new') { Time.new(iso) }
x.report('opt') { Time.match_new(iso) }

x.compare!(order: :baseline)
end

<details>

Of course, if we were to reimplement `.xmlschema` in C, we'd likely could be even faster than `.new`, but that would mean moving that method from the time gem into Ruby core, etc.