Due to the melacha of boneh (building), on Shabbat you may not replace a:

• Door onto its hinges, or
• Sliding door onto its track.

You may not replace a door on its hinges and you may not replace a sliding door onto its track on Jewish festivals.
Reason This is due to the melacha of boneh (building).
 

The International Dateline (IDL), which is 180 degrees away from Greenwich, England, crosses the Pacific ocean from north to south and divides a region of safek/doubt as to which day is Shabbat. This region's eastern boundary is a line 180 degrees east of Jerusalem, which lies between Hawaii and the US mainland; the western boundary is east of Shanghai. All countries in this region of IDL safek/doubt are island countries.
 
In a region of doubt, such as Tasmania, keep normal Shabbat (Shabbat d'rabanan) on local Saturday and keep Shabbat d'oraita on:

• West of mainland USA, but
• East of the IDL, and
• Not attached to the mainland.

• West of the IDL, but
• East of Shanghai, and
• Not attached to the mainland.

Note In all cases, you must still observe regular Shabbat on Friday night/Saturday.
Situation
You are in a place near the International Dateline (IDL) in which you are not sure which day of the week it is halachically: Shabbat or, if you are east or west of the IDL, Friday or Sunday.
What To Do
On the Friday or Sunday in question, there is no shvut (d'rabanan prohibitions, including muktza), so you may do all melacha d'rabanan WITHOUT a shinui. You may:

• Ask or tell a non-Jew to do anything, including a melacha d'rabanan or d'oraita.
• Ride in a cab or car driven by a non-Jew.

• Use electricity--except for heat or light—including turning on a fan or air conditioner (heat and light are forbidden by the Torah).
• Use the telephone. (Using a cellphone may be permissible--ask a rabbi).

• Carry from a private domain (reshut ha'yachid) to another private domain, even through a public domain (reshut ha'rabim); but you may not stop walking in the public domain and you may not put the object down in the public domain unless you use a shinui.
• There is no practical way to light candles, even using a shinui, but a non-Jew may light them for you and and you may say the blessing on the candles.
• Swim, surf, scuba dive, climb, and play all games that do not use melacha. You may not wring out clothes and if you are swimming or scuba diving, your swimsuit or wetsuit must be clean.
• Walk any distance (there is no techum Shabbat d'oraita).
• Kinyan. You may acquire items.

• Fly, including check in and getting on plane if:
  • The pilot is non-Jewish, and
  • You don't do any melacha d'oraita (including any writing) without a shinui.
• Use a computer if it automatically goes to sleep after less than 24 hours of not being used.
• Shower. However:
  • You may not use an “instant on” hot water system in which the water is heated as you use it; you may only use the hot water if it has a holding tank.
  • You may use only liquid soap; hard soap is forbidden.
• Ingest medicine (but you may not smear it on skin).
• Use some make up, such as rouge, mascara, eye shadow. You may not use lipstick.
• Open a refrigerator with light (and all other psik reisha d'la neicha lei).

• You may buy necessities on Friday or Sunday as long as:
  • The store owner is not Jewish (or if he/she is Jewish, does not write or print a receipt),
  • You do not write, and
  • There is no reshut ha'rabim.

You may also do melacha d'oraita if:

• You use a shinui (non-normal way of doing that action--this is forbidden d'rabanan on Shabbat but is allowed on the Friday or Sunday in question), OR
• Two or more people do the melacha together.

 
D'oraita, you may not:

• Cook food.

• Turn on lights (but you may turn them off).
• Carry from domains.
• Boneh – building any permanent structure.
• Write two or more letters of the alphabet.
• Drive--there is no practical way to drive using a shinui.
• Shave--there is no practical way to shave using a shinui.
• Use toothpaste (but you may use tooth-cleaning powder).
• Use skin cream--you may dab it on without smearing it.

However, you may do these following actions with a shinui on the Friday or Sunday in question, as follows:

• Cook food. You must put food in the cooking utensil first, then turn on the heat with shinui. You may turn off the heat even without a shinui.
• Turn on lights (such as with your elbow).
• Stop along the way when carrying from a private domain (reshut ha'yachid) to another private domain, even through a public domain (reshut ha'rabim). As a shinui, you may carry the object in your mouth (as long as it is not food), etc.

Note Carrying something in your pocket is NOT a shinui.

• Tear paper (such as putting toilet paper across knees and moving the knees apart).
• Write (such as with the opposite hand).

Flying East From Australia on Sunday If You Cross IDL from Friday into Saturday

Eating gefilte fish, made of fish in which bones have been removed, avoids the necessity of doing the melacha of selecting (boreir) the bones from the fish. This allows a fish course to be eaten at a Shabbat meal (which, in addition to the meat, makes the Shabbat meal special because both fish and meat would not have been commonly served in poor areas during the week).

Seder plate consists of five foods: 

Shank Bone
Shank bone, meat, or a neck represents the Passover lamb offering.

Egg
Egg represents the holiday offering (chagiga).

Bitter Herbs
Bitter herbs (maror), such as romaine, horseradish, or endive, represent the bitterness of slavery.

Charoset
Charoset (sweet mixture of nuts and fruits) reminds us of the mortar the Jews used to build the Egyptian storage cities.

Vegetable
Vegetable such as parsley or potato (karpas). The vegetable does not represent anything and is there to motivate the children to ask questions.
 

A non-kosher substance becomes kosher once it is modified and no longer has the original taste.

1. Place the tefila on your head tightly enough so it does not slip off under normal motion.
2. Center the head tefila box on your forehead (as it appears to an average person. There is no need to look in a mirror.)
3. Place the head tefila box with its front edge above your hairline (or where your hairline was when you were 13!), not further back than half-way on your skull from front to back.
4. Ideally, place the knot at the back on your occipital bone (base of your skull), but you may place it lower as long as it is still on top of your hair.
5. Say the second blessing, al mitzvat tefilin.
6. Tighten the tefila on your head and say, Baruch shem kevod malchuto l'olam va'ed
   Reason “Al mitzvat tefilin” is a questionable blessing (safek bracha).
   Note Tefilin head straps should reach at least to your navel (left strap) and mila (right strap).

Issues of boreir are almost always d'oraita, not d'rabanan, and therefore we are stringent in applying restrictions concerning boreir.
Unlike on Shabbat (when you must remove some good along with the bad so as not to violate the melacha of boreir), on Jewish festivals you may remove the bad from the good if it is easier to take the undesired food from the desired food.

You may select desired food from undesired (or inedible) substances if you follow these two rules:

• Food from other food, or
• Food from other substances.
  Note You may remove dirt from a carrot's surface by scraping the peel with a knife (a tool not specialized for separating food), but not by using a peeler.
  Exception As on Shabbat, an action necessary to eat a food normally (derech achila) does not violate the prohibition of boreir. So you may peel a food that is normally separated from its peel or shell in order to be eaten, as long as you do not use a specialized instrument to do so.

• You may peel an orange by hand, with or without a knife.
• You may remove the shells from peanuts by hand.
• You may remove the shell from a hard-boiled egg by hand.

• Remove fish bones from fish while you are eating the fish or just before eating it.
• Cut open a melon such as a cantaloupe and remove any seeds normally.

Tevila is the Hebrew word for immersion.  You must tovel (immerse in a mikva or other halachically purifying water) new utensils made of metal or other materials that require tevila unless you know that they were:

• Made by a Jew,
• Sold by a Jew, and
• Not owned by a non-Jew in between.

Toveling: Utensils: How To Tovel
To tovel a utensil, you may go to any kosher natural mikva (see section on natural mikvas) or to a mikvat keilim (a small mikva for utensils, often attached to the outside of a regular mikva building). To tovel several items, some of which require a blessing and some on which there is doubt whether a blessing is necessary, say the blessing over the item that requires the blessing and have in mind that the blessing will cover all the rest of your items.
Remember to remove all stickers, rust, etc., before you begin. Nail polish remover may help with stubborn stickers. Say the blessing al tevilat keilim and then let the item free fall through the water. Unlike with hagala, during which the item may be immersed in sections, when you tovel a utensil, the entire item must be in contact with the water at the same time, even if only for an instant.

Toveling: Utensils: What Gets Toveled?
The below chart is copied with permission from the Star-K (www.star-k.org):
 
 

Utensil	Tevila Guideline		Utensil	Tevila Guideline
Aluminum Pans, Disposable if intended to be used more than once	Tevila with Brocha		Meat Tenderizer Hammer, Metal	No Tevila
Aluminum Pans, Disposable to be used only once	Tevila w/o Brocha		Melamine	No Tevila
Blech	No Tevila		Metal Cutlery	Tevila with Brocha
Blender with metal blade on bottom	Tevila with Brocha		Metal Flour and Sugar Storage Canisters	Tevila w/o Brocha
Bone	No Tevila		Metal Pots Coated with Teflon, Enamel or Plastic	Tevila w/o Brocha
Brush, Pastry	No Tevila		Metal Spoon Specifically for Medicine	Tevila w/o Brocha
Brush for Grill, Metal	No Tevila		Microwave Turntable, Glass	Tevila w/o Brocha
Can Opener	No Tevila		Mixer Beaters	Tevila w/o Brocha
Cans, Reusable Empty if opened by a Yehudi	No Tevila		Paper	No Tevila
China, Bone	Tevila w/o Brocha		Peeler, Vegetable	Tevila with Brocha
China, Glazed	Tevila w/o Brocha		Plastic	No Tevila
Colander, Metal	Tevila with Brocha		Porcelain Enamel	Tevila w/o Brocha
Cookie Cutters, Metal	No Tevila		Racks, Cooling	Tevila w/o Brocha
Cookie Sheets, Metal	Tevila with Brocha		Racks, Oven	No Tevila
Cork Screw	No Tevila		Rolling Pins Metal or Wood	No Tevila
Corningware	Tevila w/o Brocha		Sandwich Maker	Tevila with Brocha
Crockpot Ceramic Insert	Tevila w/o Brocha		Silicone	No Tevila
Crockpot Glass Lid	Tevila w/o Brocha		Sink Racks, Stainless Steel	No Tevila
Crockpot Outside Metal Shell	No Tevila		Spatula, Metal	Tevila with Brocha
Dish Rack, Metal	No Tevila		Stoneware	Tevila w/o Brocha
Dishes, Ceramic	Tevila w/o Brocha		Stoneware, Non-Glazed	No Tevila
Earthenware, Non-Glazed Dull Finish, e.g. Flower Pot	No Tevila		Storage Utensils, Glass not brought to the table	No Tevila
George Foreman Grill	Tevila w/o Brocha		Styrofoam	No Tevila
Glass (including Pyrex, Duralex & Corelle)	Tevila with Brocha		Tea Kettle, Corelle	Tevila with Brocha
Grater, Metal used for foods that are ready to eat, eg, apples, onions	Tevila with Brocha		Toaster which will not break	Tevila w/o Brocha
Grater, Metal used only for foods that need further cooking,eg potatos	Tevila w/o Brocha		Toaster Oven rack & tray only	Tevila with Brocha
Hamburger Maker	Tevila with Brocha		Trivet, Metal	No Tevila
Hot Air Popcorn Maker, Metal	Tevila with Brocha		Waffle Iron	Tevila with Brocha
Hot Water Urn, Metal	Tevila with Brocha		Warming Tray	No Tevila
Knife, Arts & Crafts	No Tevila		Wood	No Tevila
Knife Sharpener	No Tevila		Wooden Cask with Metal Straps	Tevila w/o Brocha
Meat Thermometer	No Tevila

Selecting Good from Bad and Bad from Good
Boreir Principle #1: You may eat anything in the manner in which it is normally eaten.
ExamplePeeling an orange.
 
Boreir Principle #2: You may not use a specialized tool.
 
Boreir Principle #3: You may not remove “bad” from “good.”
What To Do  Take good (edible or desired food) from the undesired (bad) components.
Note You may do this only when you are ready to eat it or when you are preparing the food to be eaten soon afterward.
 
Note Boreir is a complicated area of halacha. Because issues of boreir are almost always from the Torah (d'oraita, not d'rabanan), we are stringent in applying restrictions concerning boreir. Consult a rabbi for specific questions.
 
Selecting Undesired from Desired Food
On Shabbat, you may not usually separate totally undesired from totally desired food in a standard way, even without a specialized tool.
    NOTE As on Jewish festivals, an action needed to eat a food normally (derech achila) does not violate the prohibition of boreir on Shabbat. So you may peel a food that is normally separated from its peel or shell in order to be eaten, as long as you do not use a specialized instrument to do so. For example, on Shabbat, you may do the following by hand without a shinu'i:

• Peel an orange
• Remove the shell of a hard-boiled egg
• Separate peanuts from their shells.

NOTE If peanut shells are then put into a container that also has unshelled peanuts, you may not remove the empty shells from that mixture!
SITUATION You want remove dirt from a carrot's surface on a Shabbat.
WHAT TO DO You may remove the dirt with an altered method (shinu'i), such as scraping the peel with a knife (which is a tool not specialized for separating food)-- but not by using a peeler.
REASON The normal way to eat the carrot is to peel it.
 Selecting Desired from Undesired Food
 
While eating food (and some time before--within the amount of time you would normally need to prepare a meal), you may select desired food from undesired (or inedible) substances by hand or non-specialized tool. You may not use a specialized implement.
EXAMPLE You may remove fish from its skeleton even before eating it, but you may not remove the skeleton from the fish (because you have removed bad from good).
NOTE Once Shabbat has begun:

• You may remove fish bones from fish while you are eating the fish, but not before you are eating the fish.
• You may cut open a melon such as a cantaloupe and shake the seeds out (this is because some of the seeds remain), or take a bite of the melon and spit out the seeds. But you may not remove any remaining seeds using your hand or an implement.

EXCEPTION If you take undesired elements along with the desired food, it is not considered to be separating:  you may use a specialized tool and it does not have to be eaten soon (within the normal food-preparation time).