ABU DHABI // Sakher Abdullah Saif never leaves home without a piece of paper and a pen in the pockets of his kandura.
He is always ready to draw an item that in many ways has defined his life for the past 10 years.
"Once they know who I am, they ask me to draw them that circle," explains the 55-year-old Emirati with a hearty laugh.
"That circle has become my life and, in some ways, my curse."
The circle he is talking about is the traditional calendar known as Al Drour. Over the years he has drawn it countless times - for museums, sheikhs, heritage clubs and even on television.
All of us lives by some kind of calendar, taking each day as an arbitrary period determined by the motion and appearances of celestial bodies such as the stars and moon.
Depending on which calendar you follow, it can change your whole direction in life and concept of time.
In the case of Mr Saif, it was his fascination with the stars, solar system and astronomy that began when he was a teenager.
It led him to rediscover one of the Arabian Gulf region's oldest calendars which, until a few decades ago, was well known among Emiratis and Gulf nationals but was in danger of being lost.
The calendar is so old, he says, that the legendary Arab navigator Ahmad Ibn Majid, who many believe was born in Julfar, Ras Al Khaimah, or Sohar, Oman, referred to it 500 years ago.
There are different versions of Al Drour. Desert Bedouin use different stars and calculations to those tribes that settled in the mountains and along the coast.
But the principle is roughly the same, using a four-season calendar that is divided by the stars and the slight movement perceived in their heliacal rising and setting each day.
One of the most important stars is Souhail, also known as Canopus. The second brightest in the sky, it inspired the use of the astronomical Canopus calendar in the Arabian Gulf for centuries.
Appearing in the sky mid-August every year, it remains visible until late winter in the Arabian Peninsula, its appearance promising the end of the hot season and the beginning of a more moderate climate.
"It is not that hard to learn, but because it has numbers and some calculations people think it is hard and don't bother to study it," says Mr Saif, who is also a civil engineer working in the oil industry as a technical adviser in production and export control.
"I never knew a hobby would turn into something like this," he adds. "I want to release user-friendly programmes to help kids learn difficult maths such as calculus, but for now I will keep drawing this circle."
On cue, he takes out his pen and a piece of paper to draw yet another Drour calendar.
"The Drour calendar is based on arbitrary 10-day units divided into 36 sections and takes into account astronomical variations as well as the weather and seasons," he explains. "It begins in August, with the appearance of Souhail star," he says, marking it on the circle.
It is a 365-day calendar, but divided into four sections representing seasons - three sections of 100 and one section of 60. The last five days are known as "Al Khams Al Masrouqa", or the five stolen days.
Each group of 100 days consists of 10 sets of 10. Each set of 10 is a der, the plural of which is drour.
The fourth period comprises six drour. The total number of days equals 360, with the remaining five "stolen days" making up the full 365-day calendar.
The first 100 days are the autumn period, known as Al Asfar, followed by 100 days winter, or Sheta, then summer, or Saif and, because this is the Gulf, a second "really hot summer" period known as Al Qaiz.
"The last five stolen days are there for the turbulence and unpredictable weather," he said.
Each der is named after the Arabic numeral system. The first der is called der Al A'shar (the 10th der), the second is der Al A'shreen (20th der) and so on until the last set of 10 days, der al Ma'ah (100th der), is reached.
"There are legends associated with the different stars, such as how Souhail killed a star out of jealousy and it ran away to the southern hemisphere and so that is why it is all alone there," Mr Saif says.
Other stars in the calendar include Thuraya, the Pleiades star cluster also known as the Seven Sisters, which traditionally heralds one of the year's biggest storms right before the summer season and just before the clusters disappear around the last week of April.
The Northern Emirates and, in general, the north of the Arabian Gulf, including Kuwait, observe seasonal winds blowing from the east to calculate their calendar, called "nourouz" or "new day" in Persian.
"Each season is associated with a certain harvest, fishing and bird migrations, pearl-diving habits and traditions," Mr Saif says.
March, for instance, is the best time for planting mint, beans and aubergines, while April is the ideal month for palm trees and corn.
"It is not just the calendar people paid attention to, but to signals from nature," he explains. "For instance, around this time of year, hodhod bird, or hoopoe, appears.
"When it used to show up on a sailor's boat, it was a good omen as it meant fish would be abundant."
September is good for watermelons and catching shrimps, while dung beetles appear now.
Next month marks the lemon and corn harvest and the appearance of seagulls. The season for "hammour khor", also known as the Epaulet grouper, falls within the five stolen days.
"It has all been calculated and charted out many centuries ago and while there are sometimes some surprises, the old methods are quite reliable," Mr Saif says.
The weather forecast for the rest of this month, based on Drour, is a continuation of the shamali and sharqi winds (north-east) until the end of the month, with lower temperatures at night but heat and humidity during the day.
Next week, from about September 20, the hours of day and night will be about equal, bringing more moderate temperatures.
Besides the Drour, Mr Saif has been working with scientists on publishing the yearly comprehensive Al Taqweem Al Hijri, an Islamic calendar, for the past 13 years.
"Most people don't ask where the names of the months in the Islamic lunar calendar came from," Mr Saif says.
Four of the months are related to months of "no killing", such as Muharram (forbidden), Rajab (to respect), Dou Al Qeeda (to settle down or sit) and Dou Al Hejja (the pilgrimage that started from the time of Ibrahim).
Other examples are Shawwal, relating to fire, the time camels pull their tails or "mating season", and Ramadan, related to "hot". Then there is Rabee Al Awal and Rabee Al Thani (spring times), then Jamad Al Awal and Jamad Al Thani (cold times).
"Unlike the Gregorian calendar, adopted in 1582, which has names of Roman Gods and rulers as its months, the Islamic calendar and even pre-Islamic calendars didn't adopt Gods and idols' names," Mr Saif says.
"It is really interesting and quite telling about the Arab culture, even in pagan times.
"The idols were a business and social habits, not something that was held that dear to the tribes."
The week in Arabic is also related to the Arabic numeral system, with Juma referring to Friday when people gather, while Sabt, related to day of rest, is also known as the Sabbath and practised in other Abrahamic religions.
"There is so much information and history in calendars," said Dr Hamid Al Naimiy, the vice chancellor for academic affairs at the University of Sharjah.
He is also a professor of astronomy and astrophysics and president of the Arab union for astronomy and space sciences.
Dr Al Naimiy is one of the authors of the Islamic calendar and, together with Mr Saif, is working on the next year's edition.
Even horoscopes are included, but Dr Al Naimiy makes his position on astrology clear: "It is an art. I don't believe in horoscopes.
"There are actually 88 constellations and within the zodiac signs, there are 13 not 12, with the 13th known as Eve."
Through his writings and lectures, Dr Al Naimiy is trying to revive this field within the Arab world.
"Arabs and Muslims pioneered the fields of astronomy, maths and physics in the golden age of Islamic civilisation, so we need to revive it all and bring it back here," he says.