perf fix Time

[mcakircali]

try to avoid std::regex

[codecov-commenter]

Codecov Report

:x: Patch coverage is 86.40000% with 17 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 65.74%. Comparing base (99c3ed6) to head (a8900f1).

Files with missing lines	Patch %	Lines
src/eckit/types/Time.cc	86.40%	17 Missing :warning:

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #142   +/-   ##
========================================
  Coverage    65.73%   65.74%           
========================================
  Files         1131     1131           
  Lines        57446    57508   +62     
  Branches      4327     4332    +5     
========================================
+ Hits         37760    37806   +46     
- Misses       19686    19702   +16     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

:rocket: New features to boost your workflow:

• :snowflake: Test Analytics: Detect flaky tests, report on failures, and find test suite problems.