ARTICLE
Rules for Time Zones
The conversion of the UTC reference time to the local date and
the local time zone is based on a set of rules stored in AS ABAP
system tables. The names of all associated tables start with TTZ .
The following database tables, whose content you can maintain using
transaction STZBD , are relevant for time zones:
The database table TTZZ contains a
list of possible time zones in the column TZONE . The entries in
the columns ZONERULE and DSTRULE refer to the rules for
the time difference of the time zone to the UTC reference time in
table TTZR and to the rules for summer time in the tables
TTZD , TTZDF , and TTZDV .
The column ZONERULE of the database table
TTZR contains a list of possible
rules for the time difference between time zones and the UTC
reference time. The columns UTCDIFF and UTCSIGN contain
the time differences to UTC and their signs, while ignoring
summer time.
The database table TTZD contains a
list of all possible summer time rules in column DSTRULE . The
column DSTDIFF contains the time difference between summer time
and winter time.
The database table TTZDF contains a
list of fixed summer time rules in column DSTRULE . The column
YEARACT contains year numbers for every year for which the rule
applies. The columns DATEFROM , TIMEFROM , DATETO ,
and TIMETO contain the date and time for the beginning and end of
summer time.
The database table TTZDV contains a
list of variable summer time rules in column DSTRULE . The column
YEARFROM contains a year number for every rule, saying in which
year the rule applies. The columns MONTHFROM , WEEKDFROM ,
WEEKDCFROM , TIMEFROM , MONTHTO , WEEKDTO ,
WEEKDCTO , and TIMETO contain the month, week, day, and time
for the beginning and end of summer time.
A correct set of rules must contain all rules specified in TTZZ
for the time difference between time zones and the UTC reference
time in TTZR and all rules specified for summer time in TTZD
. If the time difference between summer time and winter time in
TTZD is not equal to 0, the respective summer time rule must be
included in at least one of the tables TTZDF or TTZDV .
While TTZDF contains fixed dates for the switch, the date in
TTZDV is variable, because a day in a particular week of a month is
specified. The system always checks TTZDF first for the summer
time rule and then TTZDV .
Notes for Summer Time
If a time zone specifies a summer time rule with a summer time
difference not equal to 0, note the following:
If during summer time a new year starts (in the southern hemisphere),
then the year specified in the database tables TTZDF or TTZDV
identifies the beginning of the summer time, while the end is in the
following year.
The time specified for the beginning of summer time in the tables
TTZDF and TTZDV identifies the time when the clock is put
forward by the summer time difference when the winter time ends. The
first second of summer time is the time you get when you add the summer
time difference to the specified time.
When summer time begins, a time interval of the length of the summer
time difference is created, for which you can formulate a date and time,
but which does not exist as a local time and which cannot be assigned to
an UTC reference time. A local time of this type is handled in
the CONVERT INTO TIME STAMP
statement as an invalid time.
The time specified in the database tables TTZDF or TTZDV
for the end of summer time identifies the time when the clock is put
back by the summer time difference when summer time ends. The first
second of the winter time is the time you get when you subtract the
summer time difference from the specified time.
When summer time ends, a time interval of the length of the summer time
difference is created, which is passed twice as a local time (the double
hour). If you formulate a date and time for this interval, the statement
CONVERT INTO TIME STAMP
handles it as a time from summer time, by default.
Documentation extract taken from SAP system, � Copyright SAP AG. All rights reserved