Example of a time zone receiving “tz”

You can obtain the tz parameter using bitwise operations such as mathematical AND (&) and mathematical OR (|).

Below are the instructions to obtain the tz parameter for the Azores time zone (-01:00) with no DST (0x08000000).

1. Apply a mathematical AND operation to the Azores time zone (-3600) using the 0xf000ffff mask.

   • Convert the decimal signed value to binary using the two’s complement method.
   • Perform the operation:
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   -3600 & 0xf000ffff
   -268373520 
   

2. Apply a mathematical OR operation to the result using the mask corresponding to DST(0x08000000).

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   -268373520 | 0x8000000
   -134155792
   

Thus, the final value for tz is -134155792.

To retrieve the original time zone (tz) value from tz = -134155792, follow these steps:

1. Apply a mathematical AND operation to the tz parameter using the 0xffff mask:

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   -134155792 & 0xffff
   61936
   

2. If the original tz value is negative (which it is in this case), apply a mathematical OR operation to the result using the 0xffff0000 mask.

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   61936 | 0xffff0000
   -3600
   

This confirms that the original time zone value is -3600 (UTC -01:00, Azores).

Additional information

• The tz value -134155792 in hexadecimal is 0xf800f1f0.
• Applying the 0x0fff0000 mask isolates the DST component.
• A DST value of 0x08000000 indicates no DST adjustment.

Thus, the decoded time zone is UTC -01:00 (Azores) with no DST.