fread tz= default changed from "" to "UTC"

[mattdowle]

Follow up to #4464

In that case, shouldn't we plan to set tz='UTC' by default (maybe not this release, but next release?)

Yes, you were right, @MichaelChirico.

At least I did say at the bottom of this comment that I wasn't as strongly against tz='UTC' by default and that we could ask the community.

News item contains the detail.

The next release containing this change would be 1.14.0.

Merging now straight away without review. We can see if it passes GLCI, I'll start a rerun of all revdeps just to make sure, and I'll tweet asking community to test dev and raise any objections. We can keep discussing and see if any objections are raised. We can always revert this PR if necessary. Merging is necessary so that folk can test master.

Update:
GLCI passed and deployed, so folk can test master now.
Community consulted via tweet: https://twitter.com/MattDowle/status/1358011599336931328
Revdep rerun complete and looks good; i.e. no impact. These 8 are either error/warning on CRAN already for unrelated reasons, or we've communicated with maintainer before and it's a known different issue.

 ERROR   :    5 : lava mlr3pipelines reproducible rGoodData segregation 
 WARNING :    3 : crfsuite disk.frame tcR 
 NOTE    :  346 
 OK      :  650 
 TOTAL   : 1004 / 1004

cran()
         Package r-release-linux-x86_64 r-release-macos-x86_64 r-release-windows-ix86+x86_64
1:          lava                   NOTE                     OK                            OK
2: mlr3pipelines                  ERROR                     OK                         ERROR
3:  reproducible                  ERROR                     OK                         ERROR
4:     rGoodData                  ERROR                     OK                            OK
5:   segregation                     OK                     OK                            OK
6:      crfsuite                     OK                     OK                            OK
7:    disk.frame                   WARN                     OK                          WARN
8:           tcR                   WARN                   NOTE                          WARN

[codecov]

Codecov Report

Merging #4894 (11d790d) into master (d8f43cb) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4894   +/-   ##
=======================================
  Coverage   99.46%   99.46%           
=======================================
  Files          73       73           
  Lines       14414    14414           
=======================================
  Hits        14337    14337           
  Misses         77       77           

Impacted Files	Coverage Δ
R/fread.R	100.00% <ø> (ø)

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[mattdowle]

@renkun-ken Hi. Would you mind running your extra-strength go-first please? Wondering if you're ok with this default change.