backup: add time zone in examples (#17915)

br/backup-and-restore-use-cases.md

@@ -121,15 +121,15 @@ The following are two snapshot backup examples:
     ```shell
     tiup br backup full --pd="${PD_IP}:2379" \
     --storage='s3://tidb-pitr-bucket/backup-data/snapshot-20220514000000' \
-    --backupts='2022/05/14 00:00:00'
+    --backupts='2022/05/14 00:00:00 +08:00'
     ```
 
 - Run a snapshot backup at 2022/05/16 00:00:00
 
     ```shell
     tiup br backup full --pd="${PD_IP}:2379" \
     --storage='s3://tidb-pitr-bucket/backup-data/snapshot-20220516000000' \
-    --backupts='2022/05/16 00:00:00'
+    --backupts='2022/05/16 00:00:00 +08:00'
     ```
 
 ## Run PITR

br/br-snapshot-guide.md

@@ -25,14 +25,14 @@ You can back up a TiDB cluster snapshot by running the `br backup full` command.
 
 ```shell
 tiup br backup full --pd "${PD_IP}:2379" \
-    --backupts '2022-09-08 13:30:00' \
+    --backupts '2022-09-08 13:30:00 +08:00' \
     --storage "s3://backup-101/snapshot-202209081330?access-key=${access-key}&secret-access-key=${secret-access-key}" \
     --ratelimit 128 \
 ```
 
 In the preceding command:
 
-- `--backupts`: The time point of the snapshot. The format can be [TSO](/glossary.md#tso) or timestamp, such as `400036290571534337` or `2018-05-11 01:42:23`. If the data of this snapshot is garbage collected, the `br backup` command returns an error and `br` exits. If you leave this parameter unspecified, `br` picks the snapshot corresponding to the backup start time.
+- `--backupts`: The time point of the snapshot. The format can be [TSO](/glossary.md#tso) or timestamp, such as `400036290571534337` or `2018-05-11 01:42:23 +08:00`. If the data of this snapshot is garbage collected, the `br backup` command returns an error and `br` exits. When backing up using a timestamp, it is recommended to specify the time zone as well. Otherwise, `br` uses the local time zone to construct the timestamp by default, which might lead to an incorrect backup time point. If you leave this parameter unspecified, `br` picks the snapshot corresponding to the backup start time.
 - `--storage`: The storage address of the backup data. Snapshot backup supports Amazon S3, Google Cloud Storage, and Azure Blob Storage as backup storage. The preceding command uses Amazon S3 as an example. For more details, see [URI Formats of External Storage Services](/external-storage-uri.md).
 - `--ratelimit`: The maximum speed **per TiKV** performing backup tasks. The unit is in MiB/s.
 

br/br-snapshot-manual.md

@@ -34,15 +34,15 @@ You can back up the latest or specified snapshot of the TiDB cluster using the `
 ```shell
 br backup full \
     --pd "${PD_IP}:2379" \
-    --backupts '2022-09-08 13:30:00' \
+    --backupts '2024-06-28 13:30:00 +08:00' \
     --storage "s3://${backup_collection_addr}/snapshot-${date}?access-key=${access-key}&secret-access-key=${secret-access-key}" \
     --ratelimit 128 \
     --log-file backupfull.log
 ```
 
 In the preceding command:
 
-- `--backupts`: The time point of the snapshot. The format can be [TSO](/glossary.md#tso) or timestamp, such as `400036290571534337` or `2018-05-11 01:42:23`. If the data of this snapshot is garbage collected, the `br backup` command returns an error and 'br' exits. If you leave this parameter unspecified, `br` picks the snapshot corresponding to the backup start time.
+- `--backupts`: The time point of the snapshot. The format can be [TSO](/glossary.md#tso) or timestamp, such as `400036290571534337` or `2024-06-28 13:30:00 +08:00`. If the data of this snapshot is garbage collected, the `br backup` command returns an error and 'br' exits. If you leave this parameter unspecified, `br` picks the snapshot corresponding to the backup start time.
 - `--ratelimit`: The maximum speed **per TiKV** performing backup tasks. The unit is in MiB/s.
 - `--log-file`: The target file where `br` log is written.