Holidays in Guinea-Bissau

Official national public holidays. Regional and religious observances may vary by area.

About Time in Guinea-Bissau

Bissau Entered 1912 by Skipping Two Minutes and Twenty-One Seconds

The historical clock for Bissau begins at UTC−01:02:20, a local mean time derived from longitude rather than from a standardized one-hour zone.

The change came at the opening of 1912. IANA's reconstruction places the transition at 01:00 UTC on January 1. In Bissau, 23:57:39 on December 31 was followed by 00:00:00. The final two minutes and twenty-one seconds of the old local day did not occur.

The new offset was UTC−01:00. It was a small adjustment by later standards, but conceptually it was decisive: Bissau had stopped using a clock tied exactly to its own solar meridian and adopted a standardized offset.

The 1912 Change Came from a Portuguese Decree, but the Decree Date Is Not the Clock-Change Date

Historical time-zone research for Guinea-Bissau contains a useful warning about dates. Older references sometimes placed the change in May 1911 because that was when the Portuguese decree establishing standardized time was issued.

Later examination of the decree showed that the new system did not take effect in Bissau until January 1, 1912. The IANA data were corrected accordingly.

For historical timestamp work, the distinction is substantial. A law can be signed or published months before the instant when clocks actually change. Using the legislative date as the transition date would assign the wrong offset to more than half a year of local timestamps.

At New Year 1975, Guinea-Bissau Lost an Entire Hour

UTC−01:00 remained in the historical record through the end of 1974. Then the first minute of 1975 brought a much larger adjustment than the one made in 1912.

After 23:59:59 on December 31, 1974, clocks advanced directly to 01:00:00 on January 1, 1975. Midnight through 00:59:59 was skipped. Guinea-Bissau had moved onto Greenwich Mean Time, UTC+00:00.

The timing is notable because the change followed independence rather than occurring simultaneously with it. Independence was proclaimed in 1973 and recognized by Portugal in 1974; the civil clock was realigned at the beginning of the following year.

Since 1975, Africa/Bissau Has Needed No Seasonal Clock Rules

Guinea-Bissau now uses UTC+00:00 throughout the year. It has one national time zone and does not observe daylight saving time.

The IANA identifier Africa/Bissau nevertheless carries more information than the current offset alone. It preserves the earlier local mean time, the UTC−01:00 period beginning in 1912 and the one-hour jump to GMT in 1975. For a modern clock, UTC+00:00 is enough. For an archival timestamp, the date determines which clock applied.

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