Use fixed dates in test for consistent results.

Taken from upstream:

  https://github.com/timescale/timescaledb/commit/1d0670e703862b284c241ab797404f851b25b5df

diff --git a/test/expected/copy-12.out b/test/expected/copy-12.out
index 5cb28a45a2..37abf6f6ff 100644
--- a/test/expected/copy-12.out
+++ b/test/expected/copy-12.out
@@ -324,13 +324,12 @@ INSERT INTO hyper_copy_large
 SELECT time,
 random() AS value
 FROM
-generate_series(now() - INTERVAL '1 months', now() - INTERVAL '1 day',
-  INTERVAL '1 hour') AS g1(time)
+generate_series('2022-01-01', '2022-01-31', INTERVAL '1 hour') AS g1(time)
 ORDER BY time;
 SELECT COUNT(*) FROM hyper_copy_large;
  count 
 -------
-   697
+   721
 (1 row)
 
 -- Migrate data to chunks by using copy
@@ -345,7 +344,7 @@ NOTICE:  migrating data to chunks
 SELECT COUNT(*) FROM hyper_copy_large;
  count 
 -------
-   697
+   721
 (1 row)
 
 ----------------------------------------------------------------
diff --git a/test/expected/copy-13.out b/test/expected/copy-13.out
index 02bf913eff..89e16fe8e2 100644
--- a/test/expected/copy-13.out
+++ b/test/expected/copy-13.out
@@ -324,13 +324,12 @@ INSERT INTO hyper_copy_large
 SELECT time,
 random() AS value
 FROM
-generate_series(now() - INTERVAL '1 months', now() - INTERVAL '1 day',
-  INTERVAL '1 hour') AS g1(time)
+generate_series('2022-01-01', '2022-01-31', INTERVAL '1 hour') AS g1(time)
 ORDER BY time;
 SELECT COUNT(*) FROM hyper_copy_large;
  count 
 -------
-   697
+   721
 (1 row)
 
 -- Migrate data to chunks by using copy
@@ -345,7 +344,7 @@ NOTICE:  migrating data to chunks
 SELECT COUNT(*) FROM hyper_copy_large;
  count 
 -------
-   697
+   721
 (1 row)
 
 ----------------------------------------------------------------
diff --git a/test/expected/copy-14.out b/test/expected/copy-14.out
index 02bf913eff..89e16fe8e2 100644
--- a/test/expected/copy-14.out
+++ b/test/expected/copy-14.out
@@ -324,13 +324,12 @@ INSERT INTO hyper_copy_large
 SELECT time,
 random() AS value
 FROM
-generate_series(now() - INTERVAL '1 months', now() - INTERVAL '1 day',
-  INTERVAL '1 hour') AS g1(time)
+generate_series('2022-01-01', '2022-01-31', INTERVAL '1 hour') AS g1(time)
 ORDER BY time;
 SELECT COUNT(*) FROM hyper_copy_large;
  count 
 -------
-   697
+   721
 (1 row)
 
 -- Migrate data to chunks by using copy
@@ -345,7 +344,7 @@ NOTICE:  migrating data to chunks
 SELECT COUNT(*) FROM hyper_copy_large;
  count 
 -------
-   697
+   721
 (1 row)
 
 ----------------------------------------------------------------
diff --git a/test/sql/copy.sql.in b/test/sql/copy.sql.in
index 91402c2ab8..bba4265064 100644
--- a/test/sql/copy.sql.in
+++ b/test/sql/copy.sql.in
@@ -276,8 +276,7 @@ INSERT INTO hyper_copy_large
 SELECT time,
 random() AS value
 FROM
-generate_series(now() - INTERVAL '1 months', now() - INTERVAL '1 day',
-  INTERVAL '1 hour') AS g1(time)
+generate_series('2022-01-01', '2022-01-31', INTERVAL '1 hour') AS g1(time)
 ORDER BY time;
 
 SELECT COUNT(*) FROM hyper_copy_large;
 gnu/build/accounts.scm (allocate-passwd): Add comment as to why
'real-name' is taken from PREVIOUS.  Add (not system?) to the
condition.
* gnu/system.scm (operating-system-etc-service) <login.defs>: Add
"CHFN_RESTRICT".
* gnu/system.scm (%setuid-programs): Add "chfn".
* gnu/system/pam.scm (base-pam-services): Add "chfn".
* doc/guix.texi (User Accounts): Document it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-08-17 01:10:25 +0300'>2021-08-17</span></td><td><a href='/guix/commit/gnu/system/pam.scm?id=b948ab8b56ac238e7a774625b8f971d28aee6055'>services: slim: Add pam-gnupg support.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/pam.scm (unix-pam-service): Add account and session PAM entries
for pam-gnupg.  Don't pass "#f" to "allow-root?" argument, because "lambda*"
already does this by default.
* doc/guix.texi (X Window): Document this.
* gnu/services/xorg.scm (&lt;slim-configuration&gt;)[gnupg?]: New record field.
(slim-pam-service): Pass "#:gnupg?" argument to "unix-pam-service".
</span></span></td><td>Oleg Pykhalov</td></tr>
<tr><td><span title='2020-05-08 16:30:50 +0200'>2020-05-08</span></td><td><a href='/guix/commit/gnu/system/pam.scm?id=dd0804c67e99914eecc471fdb92f4220425a1cbc'>services: Add descriptions.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/dbus.scm (polkit-service-type)[description]: New field.
* gnu/services/dict.scm (dicod-service-type)[description]: New field.
* gnu/services/dns.scm (knot-service-type)[description]: New field.
* gnu/services/networking.scm (dhcpd-service-type)[description]: New field.
* gnu/services/shepherd.scm (shepherd-root-service-type)[description]:
New field.
* gnu/services/xorg.scm (slim-service-type)[description]: New field.
(screen-locker-service-type)[description]: New field.
* gnu/system/pam.scm (pam-root-service-type)[description]: New field.
* gnu/system/shadow.scm (account-service-type)[description]: New field.
</span></span></td><td>Ludovic Courtès</td></tr>